Lateral Posterior Complex Research Articles

Biomechanical Analysis of Stability of Palmar Lateral Joint Capsule Ligament Complex of a Track and Field Athlete

This study is to explore the influence of palmar lateral joint capsule ligament complex on dorsal stretching stability of wrist lateral joint and to analyze its biomechanical principle, so as to provide reference for clinical medicine. To study the biomechanical characteristics of palmar lateral joint capsule posterior ligament complex, in this study we selected 8 freshly donated body upper limbs including 5 left ones and 3 right ones as research objects. By cutting off forearms and hand soft tissues and leaving wrist lateral joint capsule ligaments, the complex model was made, which can be used as normal sample. Extending from styloid process of radius to styloid process of ulna, we operated on distal ulna and cut off palmar lateral joint capsule ligament complex along an arc line and regarded it as a damaged sample. Through simulating actual clinical operation, the sample was repaired using an external fixation and analyzed according to wrist joint displacement load values. Results showed that regarding the same sample, the comparison of different displacement points was of statistical significance. In all, palmar wrist lateral joint capsule ligament complex is of vital importance, which is a key structure that determines the stability of wrist joint. Once the complex is injured, it will cause extremely serious consequences in which the most significant one is the wrist joint instability. In clinical practice, it cannot achieve very satisfactory effect by only repairing palmar lateral joint capsule ligament complex. By only relying on a transarticular external fixator, the complex can be successfully repaired and thus the complex injury displacement can be avoided and wrist joint stability be secured.

Thalamocortical Projection Neuron and Interneuron Numbers in the Visual Thalamic Nuclei of the Adult C57BL/6 Mouse.

A key parameter to constrain predictive, bottom-up circuit models of a given brain domain is the number and position of the neuronal populations involved. These include not only the neurons whose bodies reside within the domain, but also the neurons in distant regions that innervate the domain. The mouse visual cortex receives its main subcortical input from the dorsal lateral geniculate nucleus (dLGN) and the lateral posterior (LP) complex of the thalamus. The latter consists of three different nuclei: lateral posterior lateral (LPL), lateral posterior medial rostral (LPMR), and lateral posterior medial caudal (LPMC), each exhibiting specific patterns of connections with the various visual cortical areas. Here, we have determined the number of thalamocortical projection neurons and interneurons in the LP complex and dLGN of the adult C57BL/6 male mouse. We combined Nissl staining and histochemical and immunolabeling methods for consistently delineating nuclei borders, and applied unbiased stereological cell counting methods. Thalamic interneurons were identified using GABA immunolabeling. The C57BL/6 dLGN contains ∼21,200 neurons, while LP complex contains ∼31,000 total neurons. The dLGN and LP are the only nuclei of the mouse dorsal thalamus containing substantial numbers GABA-immunoreactive interneurons. These interneurons, however, are scarcer than previously estimated; they are 5.6% of dLGN neurons and just 1.9% of the LP neurons. It can be thus inferred that the dLGN contains ∼20,000 and the LP complex ∼30,400 thalamocortical projection neurons (∼12,000 in LPL, 15,200 in LPMR, and 4,200 in LPMC). The present dataset is relevant for constraining models of mouse visual thalamocortical circuits, as well as for quantitative comparisons between genetically modified mouse strains, or across species.

Beta activity: a carrier for visual attention

The alpha (8-13 Hz), beta (15-25 Hz) and gamma (30-60 Hz) bands of the EEG have been long studied clinically because of their putative functional importance. Old experimental results indicate that repetitive stimulation of the visual pathway evokes synchronous responses at the cortical level with a gain that depends on frequency; oscillations within relevant bands are less damped at subsequent processing levels than others. Our current results show in the cat that cortico-geniculate feedback has a build-in potentiation mechanism that operates at around the beta frequency and activates thalamic cells thus lowering the threshold for visual information transmission. We have also shown that enhanced beta activity is propagated along this feedback pathway solely during attentive visual behavior. This activity consists of 300-1000 ms bursts that correlate in time with gamma oscillatory events. Beta-bursting activity spreads to all investigated visual centers, including the lateral posterior and pulvinar complex and higher cortical areas. Other supporting data are discussed that are concerned with the enhanced beta activity during attentive-like behavior of various species, including humans. Finally, we put forward a general hypothesis which attributes the appearance of oscillations within the alpha, beta and gamma bands to different activation states of the visual system. According to this hypothesis, alpha activity characterizes idle arousal of the system, while beta bursts shift the system to an attention state that consequently allows for gamma synchronization and perception.

Spatial frequency processing in posteromedial lateral suprasylvian cortex does not depend on the projections from the striate-recipient zone of the cat's lateral posterior-pulvinar complex

It is generally considered that the posteromedial part of the cat's lateral suprasylvian cortex is involved in the analysis of image motion. The main afferents of the posteromedial lateral suprasylvian cortex come from a direct retinogeniculate pathway and indirect retinotectal and retino-geniculo-cortical pathways. Removal of the primary visual cortex does not affect the spatial and temporal processing of suprasylvian cortex cells suggesting that these properties are derived from thalamic input. We have investigated the possibility that the striate-recipient zone of the lateral posterior nucleus-pulvinar complex may be responsible for the spatial (and temporal) frequency processing in suprasylvian cortex since these two regions establish strong bidirectional connections and share many visual properties. Experiments were done on anaesthetized normal adult cats. Visual responses in posteromedial lateral suprasylvian cortex were recorded before, during, and after the deactivation of the lateral part of the lateral posterior nucleus accomplished by the injection of lidocaine or GABA. Results can be summarized as follows. A total of 64 cells was tested. Out of this number, 11 units were affected by the deactivation of the lateral part of lateral posterior nucleus and one cell, by the blockade of pulvinar. For all cells, except one, the effect consisted in a global reduction of the evoked discharge rate suggesting that the thalamo-suprasylvian cortex projections are excitatory in nature. We did not find any significant differences in the optimal spatial frequency, nor in the width of the tuning function, whether the grating was presented at half- or saturation contrast. In addition, there were no significant differences between the low- and high cut-off spatial frequency values computed before and after the deactivation of the lateral posterior nucleus. No specific changes were observed in the contrast sensitivity function of the posteromedial lateral suprasylvian cortex cells. Similar results were observed with respect to the temporal frequency tuning functions. Deactivating the lateral posterior nucleus did not modify the direction selectivity nor the organization of the subregions of the lateral suprasylvian cortex “classical” receptive fields. The absence of strong changes in posteromedial lateral suprasylvian cortex cell response properties following the functional blockade of the lateral posterior nucleus suggests that the projections from this part of the thalamus are not essential to generate the spatial characteristics of most posteromedial lateral suprasylvian cortex receptive fields. These properties may be derived from other thalamic inputs (e.g., medial interlaminar nucleus) and/or from the intrinsic computation of the afferent signals within the lateral suprasylvian cortex. On the other hand, it is possible that the lateral posterior nucleus–lateral suprasylvian cortex loop may be involved in other functions such as the analysis of complex motion as suggested by the findings from our and other groups.

Recurrent inhibitory interneurons of the Rabbit's lateral posterior-pulvinar complex.

We recorded from 118 neurons in the visual sector of the thalamic reticular nucleus (TRN) in anesthetized rabbits. Cells were identified by their location and characteristic burst responses to stimulation of the primary visual cortex (Cx) and optic chiasm (OX) and were classified into two groups. Type I cells had relatively short latencies from both OX and Cx stimulation, and the latency from OX was always longer than from Cx. In contrast, type II cells had much longer latencies after OX and Cx stimulation, and the latency from OX was always shorter than from Cx. Type I cells were located in the dorsal part of TRN, whereas type II cells were located in the ventral part of TRN. The physiological properties and location of type I TRN cells indicate that they are recurrent inhibitory interneurons of the dorsal lateral geniculate nucleus (LGN). Type II TRN cells most likely function as recurrent inhibitory interneurons for the lateral posterior nucleus-pulvinar complex (LP) because they could be activated antidromically by LP stimulation and orthodromically activated via axonal collaterals of LP cells. Type II TRN cells exhibited a prolonged depression after Cx or OX stimulation. Intracellular recordings showed that a prolonged inhibitory postsynaptic potential was evoked by Cx or OX stimulation. Therefore, these recurrent interneurons of LP, type II cells form mutual inhibitory connections just like those recurrent interneurons of LGN, type I cells. Our data suggest that the geniculocortical and extrageniculate visual pathways have similar recurrent inhibitory circuits.

KNEE PAIN - MENISCUS TEAR 829

HISTORY - A 23-year-old senior male basketball player for a Division I university landed after an attempted blocked shot and felt intense pain over the posterior-lateral aspect of his knee. He did not feel a pop or have complaints of instability. He had no previous history of knee pain or injury. The fifth year senior wanted to complete his final season if possible. PHYSICAL EXAM - The athlete was evaluated at courtside by the athletic trainer and in the training room by the team physician. His primary complaint was of pain and inability to fully extend his knee. Range of motion was 15°-60° limited by pain. No gross effusion was present. He was focally tender over the posterior lateral joint line. Ligamentous stability appeared to be intact with a negative Lachman's, negative posterior sag, negative external rotation recurvatum, and negative laxity to varus and valgus stress at 0° and 30°. McMurray's examination instituted pain laterally but was not complete secondary to limited range of motion. DIFFERENTIAL DIAGNOSIS: Lateral meniscus tear, 2. Posterior-lateral complex injury, 3. Popliteal tendon rupture, 4. Lateral collateral ligament strain, 5. Fracture or bone bruise. TEST AND RESULTS: Plain radiographs were negative for fracture or bony pathology. Magnetic resonance imaging revealed a peripheral tear of the entire posterior horn of the lateral meniscus and Grade I changes in the lateral collateral ligament and posterior lateral complex. FINAL DIAGNOSIS: After review of the test results with the athlete, his family, and his athletic trainer, he was taken to surgery for arthroscopy of his knee. A large bucket handle tear of his posterior meniscus was identified locked in the intercondylar notch. The unstable fragment comprised 60-70% of his entire meniscus and 100% of his posterior horn. Meniscal repair was selected over meniscectomy due to the peripheral nature and overwhelming size of the tear. An accelerated aggressive rehabilitation allowing full weight-bearing and full range of motion immediately was instituted. However, he was restricted from twisting and cutting activities for two months. TREATMENT: While meniscus tears are not an uncommon injury in elite athletes, they do present a difficult dilemma in recommendation and treatment options for coaches, athletic trainers, team physicians, and orthopaedic surgeons. This case notes an athlete playing in his final collegiate season who is an important cog in his team's success. The player, coach, athletic trainer, and physician all would like to have the athlete back as soon as possible which would imply partial meniscectomy. Nonetheless, due to the likelihood of early degenerative arthritis with a nearly complete meniscectomy, a meniscal repair with its associated longer rehabilitation would best serve this patient in the long run.

Early morphological changes in the thalamocortical projection onto the parietal cortex following ablation of the motor cortex in the cat.

Following a previous report that the cerebellar-induced cerebral response in the parietal cortex changes acutely after ablation of the frontal motor cortex, the present experiments tested whether morphological changes of the thalamo-parietal projection occur after ablation of the motor cortex. Anterograde and retrograde tracing with wheat germ agglutinin conjugated with horseradish peroxidase was used in intact and lesioned cats. The thalamocortical projection was labeled anterogradely by tracer injection into the thalamic ventral anterior and ventral lateral (VA-VL) nuclear complex that mainly relays the cerebello-cerebral projection, and thalamic neurons were labeled retrogradely by injection of the tracer into the parietal cortex. The labeled terminals in the parietal cortex of the intact animals were distributed densely in layer I and sparsely in layers III-IV, whereas those of the lesioned animals were distributed densely in layers I and III-IV. The distribution of the retrogradely labeled neurons after multiple tracer injections in layers III-IV of the parietal cortex was different in the intact and lesioned cats. In the intact animals, the labeled neurons were distributed sparsely in the central lateral nucleus and in the lateral posterior and pulvinar nuclear complex. In contrast, after ablation of the frontal cortex, the labeled neurons were also observed in the VA-VL nuclear complex. These differences between the intact and lesioned animals were detectable within 48 h after the lesion.

Responses to moving texture patterns of cells in the striate-recipient zone of the cat's lateral posterior-pulvinar complex.

We have studied the response properties of cells in the lateral part of the lateral posterior nucleus or striate-recipient zone (LPl) of the lateral posterior nucleus-pulvinar complex to the motion of textured patterns [visual noise]. Our purpose was to determine basic noise response characteristics and to compare these properties to that of cells in area 17 known to project to the LPl. Practically all LPl cells (87%) responded to the motion of visual noise. The evoked discharges were either sustained or characterized by several bursts. On average, as found in cortex, LPl neurons were more broadly tuned for the direction of noise than that of gratings (bandwidths of 49 and 36 degrees, respectively; t-test, P < 0.005). Noise tuning function in LPl was comparable to that found in cortex (mean of 48 degrees). One third of the LPl units did not exhibit any preferences for drift direction of noise. Such cells were virtually not encountered in the striate cortex. This group of LPl cells was generally not tuned for grating direction. For practically all LPl cells, responses to noise varied as a function of drift velocity. The mean optimal velocity was 27.5 degrees/s with mean bandwidth of 2.5 octaves. LPl cells were sensitive to a broader range of velocities than complex cells in area 17. The results of the present study showed that visual noise is an appropriate stimulus for studying motion sensitivity of cells in the LPl. It also revealed that the noise response properties, such as direction and velocity tuning functions, are very similar to those reported in the striate cortex. The exact contribution of area 17 in the visual noise responsiveness of LPl cells remains to be determined. This study provides additional evidence that the lateral posterior nucleus-pulvinar complex may be involved in many aspects of visual processing.

Retinotopic organization within the lateral posterior complex of the cat.

Electrophysiological mapping methods were employed to systematically study the retinotopic organization within the cat's lateral posterior complex (LP). Visual responses were recorded in all the major subdivisions of the LP as well as in several adjoining cell groups. Specifically, separate representations of the visual field were identified for pulvinar, zones LP1-c, LP1-r, LPi, and LPm. Partial representations of the visual field were also evident in the geniculate wing, subdivisions of the lateral posterior shell, the inferior division of the posterior nuclear group, the suprageniculate nucleus, and the central lateral nucleus. Sufficient mapping observations were made to define the internal organization of major visual representations. Additionally, there was a very close correspondence between the mapping observations when they were compared with the cytoarchitectural criteria for recognizing functional cell groups (Updyke: J. Comp. Neurol. 219:143-181, '83).

Does the pulvinar-LP complex contribute to motor programming?

Extracellular unit recording studies in the pulvinar lateral posterior complex (Pul-LP) of behaving monkeys have shown a response property not previously reported. In monkeys performing aimed arm reaching movements towards frontally located targets some cells showed a change in activity beginning 495±84 ms before the onset of the reaching movement. This change in frequency precedes that observed in primary motor and parietal posterior cortex for reaching movements. These findings seem to indicate the involvement of the Pul-LP in motor functions and suggest its possible contribution to motor programming.

Immunohistochemistry of aromatic L-amino acid decarboxylase in the cat forebrain.

The topographic distribution of aromatic L-amino acid decarboxylase (AADC)-immunoreactive (IR) neurons was investigated in the cat hypothalamus, limbic areas, and thalamus by using specific antiserum raised against porcine kidney AADC. The perikarya and main axons were mapped on an atlas in ten cross-sectional drawings from A8 to A16 of the Horsley Clarke stereotaxic plane. AADC-IR neurons were widely distributed in the anterior brain. They were identified in the posterior hypothalamic area, rostral arcuate nucleus of the hypothalamus, dorsal hypothalamic area, and periventricular complex of the hypothalamus, which contain tyrosine hydroxylase (TH)-IR cells and are known as A11 to A14 dopaminergic cell groups. AADC-IR perikarya were also found in the other hypothalamic areas where few or no TH-IR cells have been reported: the supramamillary nucleus, tuberomamillary nucleus, pre- and anterior mamillary nuclei, caudal arcuate nucleus, dorsal hypothalamic area immediately ventral to the mamillothalamic tract, anterior hypothalamic area, area of the tuber cinereum, retrochiasmatic area, preoptic area, suprachiasmatic and dorsal chiasmatic nuclei. We also identified them in the anterior commissure nucleus, bed nucleus of the stria terminalis, stria terminalis, medial and central amygdaloid nuclei, lateral septal nucleus, and nucleus of the diagonal band of Broca. AADC-IR neurons were localized in the ventromedial part of the thalamus, lateral posterior complex, paracentral nucleus and lateral dorsal nucleus of the thalamus, medial habenula, parafascicular nucleus, subparafascicular nucleus, and periaqueductal gray. Conversely, we detected only a few AADC-IR cells in the supraoptic nucleus whose rostral portion contains TH-IR perikarya. Comments are made on the relative localizations of the AADC-IR and TH-IR neurons, on species differences between the cat and rat, as well as on the possible physiological functions of the enzyme AADC.

Projections of cholinergic and non-cholinergic neurons of the brainstem core to relay and associational thalamic nuclei in the cat and macaque monkey

The projections of brainstem core neurons to relay and associational thalamic nuclei were studied in the cat and macaque monkey by combining the retrograde transport of wheat germ agglulinin conjugated with horseradish peroxidase with choline acetyltransferase immunohistochemistry.All major sensory (medial geniculate. lateral geniculate, ventrobasal). motor (venlroanterior. ventrolateral. ventromedial), associational (mediodorsal, pulvinar, lateral posterior) and limbic (anteromedial.,interoventral) thalamic nuclei of the cat were found to receive projections from cholinergic neurons located in the peribrachial area of the pedunculopontine nucleus and in the laterodorsal tegmental nucleus as well as from non-cholinergic neurons in the rostral (perirubral) part of the central tegmental mesencephalic field. Specific relay nuclei receive less than 10%) of their brainstem afferents from non-cholinergic neurons located at rostral midbrain levels and receive 85 96% of their brainstem innervation from a region at midbrain pontinc junction where the cholinergic perihrachial area and laterodorsal tegmental nucleus are maximally developed. of the total number of horseradish peroxidase-positive brainstem neurons seen after injections in various specific relay nuclei, the double-labeled (horseradish peroxidase + choline acetyltransferase) neurons represent approximately 70 85%. Three to eight times more numerous horseradish peroxidase-labeled brainstem cells were found after injections in associational (mediodorsal and pulvinar lateral posterior complex) and diffusely cortically projecting (ventromedial) thalamic nuclei of cat than after injections in specific relay nuclei. The striking retrograde cell labeling observed after injections in nuclei with associative functions and widespread cortical projections was due to massive afferentation from non-cholinergic parts of the midbrain and pontine reticular formation, on both ipsi- and contralateral sides.After wheat germ agglutinin horseradish peroxidase injections in the associative pulvinar lateral posterior complex and mediodorsal nucleus of Macaca sylvana.. 45 50% of horseradish peroxidase-positive brainstem peribrachial neurons were also choline acetyltransferase-positive. While cells in the medial part of the cholinergic peribrachial area were found to project especially towards the pulvinar lateral posterior nuclear complex in monkey, the retrograde cell labeling seen after the mediodorsal injection was mostly confined to the lateral part of both dorsal and ventral aspects of the peribrachial area.These findings support the role played by cholinergic and non-cholinergic hrainstem thalamic projections in various tonic and phasic events of behavioral slates of vigilance.

Retinal projections in two Australian polyprotodont marsupials: kowari, Dasyuroides byrnei, and fat-tailed dunnart, Sminthopsis crassicaudata (Dasyuridae).

Retinal projections were examined in two small dasyurids, the kowari and the fat-tailed dunnart, following injections of 3H-proline into one eye. In both animals retinal fibres terminate in the dorsal and ventral lateral geniculate nuclei (LGd, LGv), the lateral posterior nuclear complex, the pretectum, the superior colliculus, the suprachiasmatic nucleus of the hypothalamus and the nuclei of the accessory optic system. The lateroposterior thalamic complex and the accessory optic nuclei receive projections from the contralateral eye only; the remaining centres receive bilateral inputs. Both LGd contain an undifferentiated beta or medial segment and an alpha or lateral segment that comprises further cellular sublaminae, 4 in the kowari and 3 in the dunnart. There is substantial overlap of crossed and uncrossed terminals in both segments, though in each animal a narrow cell lamina next to the optic tract receives only crossed projections and the lateral part of the beta segment receives only uncrossed projections. There is a cell-sparse zone within the alpha segment that receives a predominately uncrossed projection in the kowari and a crossed projection in the dunnart. In both marsupials the density of crossed and uncrossed terminals is equal, a feature of dasyurid quolls but not of another dasyurid, the Tasmanian devil. Additionally, retinal terminals do not form dense clusters within the LGd neuropil. This feature is characteristic of quolls, but not of other mammals, marsupial or placental, all of which display LGd terminal clusters. These findings suggest that the functional organisation of the LGd in these dasyurids may differ from that found in other marsupials.

Chapter 7: The lateral posterior complex of the cat: studies of the functional organization

Publisher Summary This chapter describes the functional organization of the lateral posterior complex of the cat. The complex organization of the extrageniculate visual thalamus has historically resisted analysis and has inspired several sets of terminologies and divisional schemes. The number of specific subnuclei and the terminology to be applied to these areas continue to be actively debated. One of the major obstacles to analyzing this region has been the difficulty in identifying nuclear borders. Investigators have also argued that topographically organized projections can be used to define functional subdivisions. A systematic representation of the visual world has been identified for the lateral posterior region, and this represents a further step toward understanding the integrative role of the pulvinar-lateral posterior (LP) complex. It has also been widely shown that the visual cortex and the LP complex share reciprocal projections. Adding to the integrative role of the LP complex is another significant and unanticipated set of projections. Understanding the nature of thalamic influences on these various sensory pathways requires an interpretation of the number of functional areas in the posterior thalamus.

Organization of thalamic projections in the nucleus accumbens and the caudate nucleus in cats and its relation with hippocampal and other subcortical afferents.

The organization of thalamic projections in the nucleus accumbens (NA) and the caudate nucleus of cats and its relation to other subcortical striatal afferents were studied with a retrograde tracing technique by use of lectin-conjugated horseradish peroxidase. The study showed that the paraventricular and medial parafascicular nuclei (PF) of the thalamus project to the medial NA and the parataenial and medial PF project to the lateral NA. The ventral tegmental area and substantia nigra pars dorsalis (SNpd) project to medial and lateral NA. The midline thalamic nuclei, rostral intralaminar nuclei, ventroanterior nucleus, medial and lateral PF, lateral posterior complex, and nucleus limitans project to medial caudate nucleus. The most medial substantia nigra pars compacta (SNpc) and rostral SNpd project to medial caudate nucleus. The center median, ventrolateral, and the central lateral nuclei of thalamus, SNpc, and SNpd project to lateral caudate nucleus. These results suggest that the thalamic and subcortical nuclei known to connect with the limbic and frontal cortices project to NA and medial caudate nucleus. Those thalamic nuclei connected with the motor system project to lateral caudate nucleus. The hippocampus projects selectively to medial NA. The amygdala, raphe, and other mesencephalic nuclei project only to NA and medial caudate nucleus. The organization of hippocampal, amygdala, and other subcortical afferents suggests that NA and caudate nucleus can be separated into medial "limbic" and lateral nonlimbic "sensory-motor" compartments. A brief review of the distribution pattern of some neurotransmitters, neuropeptides, and their receptors and behavior studies provides additional support to the concept that the striatum can be divided into several subcompartments.

Topographic and cytoarchitectonic organization of thalamic neurons related to their targets in low-, middle-, and high-frequency representations in cat auditory cortex.

We studied the topographic organization of thalamic projections upon different ranges of cortical frequency representation. Thalamic neurons were labeled by injecting horseradish peroxidase (HRP) or tritiated bovine serum albumin into auditory cortex. Injections in individual brains were confined to the same range of frequency representation, and distributed through three or four tonotopic cortical fields in order to label as much of the thalamic projection upon a limited range of frequency representation as practicable. Low, middle, and high ranges of the frequency representation were injected in different brains. The spatial organizations of arrays of labeled neurons are described, and each array is divided into a ventral division and lateral posterior complex (lateral part of the posterior thalamic group), both composed mainly of small cells; and a medial division, composed mainly of medium and large cells. The ventral and medial divisions (located laterally and medially within the medial geniculate body (MGB), respectively), both contact the lateral posterior complex which is located rostrally. The HRP cytoarchitecture of the three divisions is described, and the portions of the ventral division corresponding with the physiologically and cytoarchitectonically defined ventral nucleus are identified. Relatively few labeled neurons were found within other thalamic areas. The topographic organizations of the ventral division (and its tonotopic subdivision, the ventral nucleus), the lateral posterior complex (also tonotopically organized), and the medial division are described. There are planar and concentric components of the topographic organization in the ventral nucleus. Within the planar component, the low-frequency area is located laterally and the high-frequency area is located rostromedially. Within the concentric component, the low-frequency area is located centrally and the high-frequency area is located peripherally. Low-, middle-, and high-frequency areas course without interruption through the planar and concentric components. In the lateral posterior complex, the low-frequency area is located rostrally, and the high-frequency area is located caudally adjoining the high-frequency area in the ventral nucleus. The topographic organizations of the ventral nucleus and lateral posterior complex are consistent with tonotopic maps of these regions. The medium- and large-cell portion of the medial division is also topographically organized, although there may be more overlap among low-, middle-, and high-frequency arrays than in the ventral nucleus.(ABSTRACT TRUNCATED AT 400 WORDS)

The thalamostriatal projection in the cat.

The organization of the projections from the intralaminar and other thalamic nuclei to the caudate nucleus (CD), putamen (PU), nucleus accumbens (Acc), and olfactory tubercle (TO) were examined in the cat by autoradiography after deposits of 3H-amino acids in individual thalamic nuclei and by retrograde cell labeling after intrastriatal deposits of wheat-germ-conjugated horseradish peroxidase. All of the rostral intralaminar nuclei, here considered to include the central lateral (CL), paracentral (PC), central medial (CeM), and rhomboid nuclei (Rh), project to the striatum. Projections closely associated with those of the rostral intralaminar group arise from cells of the paraventricular nucleus (PV) and a region lateral to the stria medullaris. These nuclei, which roughly form a ring around the mediodorsal nucleus, project in a highly particular, but loosely arranged topographic pattern to all parts of the striatum. The medially located cells in Rh, PV, and those alongside the stria medullaris project mainly to medial parts of Acc and CD; the dorsolaterally located cells of CL project mainly to the dorsolateral parts of CD and PU; cells in PC and CeM project to progressively more ventral and medial parts of CD and PU, and the lateral part of Acc. Superimposed on this projection from the rostral intralaminar region is the projection from the caudal intralaminar group including the centromedian (CM), parafascicular (PF), and subparafascicular nuclei (subPF). Together these nuclei project in a loosely but specifically organized topography to the entire striatum. The lateral and dorsal parts of CD and PU receive fibers mainly from CM. Ventral and medial parts of CD and PU and Acc receive fibers mainly from PF; TO receives fibers from subPF and the ventral part of PF. Several nuclei in the lateral nuclear mass of the thalamus also project to particular parts of the striatum. Thus, cells in the rostromedial part of the ventral anterior nucleus project to the head of CD and some cells in the rostral part of the ventromedial nucleus project to the head of CD and to PU. Several cells scattered in the lateral posterior complex project to lateral parts of the head of CD, and cells in the rostral extension of the medial subdivision of the posterior nuclear complex project to lateral parts of the head and body of CD. Finally, several cells of the paratenial nucleus project selectively to Acc. These data provide a detailed map of the total thalamostriatal projection in the cat and, hence, form a basis for more specific functional questions about this poorly understood system.

A reevaluation of the functional organization and cytoarchitecture of the feline lateral posterior complex, with observations on adjoining cell groups.

The organization of the cat's lateral posterior complex was reevaluated and its cytoarchitecture described. Analysis of visual representations within the complex confirmed that the pulvinar, lateral zone (LPL), and interjacent zone (LPi) correspond to separate representations of the visual field and established that the zones exhibit heterogeneous connections as a result of retinotopic interconnections with extrastriate areas which represent varying amounts of the visual field. A common system of visual representation extending through layers with differing anatomical connections was identified within zone LPL. The concept of an "isorepresentation cord" was introduced to describe these variable correspondences between sensory representations and connectional relationships. Isorepresentation cords are conceived as holding in common representation of a common locus on a sensory surface without functioning as a unit with respect to connections. Visual representations within the lateral posterior complex consist of many such cords arranged in orderly array. Zone LPm (medial) was also delineated more accurately on the basis of its connections with the ectosylvian visual area. Analysis of termination patterns which occupy boundary regions adjacent to and between the principal zones further established the existence of a collection of cell groups which form a thin, irregular shell investing the principal zones. The identification of these additional cell groups and the recognition of connectional heterogeneity within the principal zones of the complex made it possible to identify and describe the subtle cytoarchitectural differences which characterize the subdivisions of the lateral posterior complex and their boundaries with adjoining nuclear groups. The present findings are discussed with respect to the functions of the lateral posterior complex in interconnecting cortical visual and visuomotor areas, and with respect to the conceptual issues raised by variable correspondences between sensory representations and connectional relationships within thalamus.

Projections from visual areas of the middle suprasylvian sulcus onto the lateral posterior complex and adjacent thalamic nuclei in cat.

The distribution of corticothalamic projections from lateral suprasylvian areas AMLS, PMLS, ALLS, and PLLS was investigated with the autoradiographic method. Areas AMLS and PMLS were both found to project retinotopically upon the medial interlaminar nucleus and the lateral and pulvinar zones of the lateral posterior complex, as well as to the ventral lateral geniculate nucleus, intralaminar nuclei, and thalamic reticular complex. Retinotopic projections to the dorsal lateral geniculate nucleus were demonstrated from PMLS but not AMLS, and projections to zona incerta were demonstrated from AMLS but not PMLS. Areas PLLS and ALLS were both found to project retinotopically upon the interjacent zone of the lateral posterior complex, as well as to the intermediate and suprageniculate divisions of the posterior nuclear group, the magnocellular division of the medial geniculate complex, the thalamic reticular complex, and central lateral nucleus. Area ALLS was also found to project onto the dorsal division of the medial geniculate complex and lateral division of the posterior nuclear group. Differences between the four cortical areas in the pattern and density of their thalamic projections supports the parcellation of these areas as proposed by Palmer et al. ('78). The projection patterns of areas PMLS, AMLS, PLLS, and ALLS were found to respect the boundaries of the zones of the lateral posterior complex, which had been identified and defined previously (Updyke, '77), and the results thus support the hypothesis that these zones are the functional units of organization of visual traffic between the cat's extrastriate visual areas.

Projections of the pulvinar-lateral posterior complex to visual cortical areas in the cat

The projections of the pulvinar-lateral posterior complex of the cat were studied using the autoradiographic tracing method and related to 15 previously defined cortical areas. The results indicate that each of three separate zones within the pulvinar-lateral posterior complex has a different pattern of projection. The most lateral zone, the pulvinar, sends fibers to at least seven cortical areas, most of which are known to have input from other visual areas within the brain: the splenial visual area, the cingulate gyrus, and areas 5, 7, 19, 20a and 21a. A zone located just medial to the pulvinar, the lateral division of the lateral posterior complex, projects to at least eight visual areas in the cortex: areas 17, 18, 19, 20a, 21a, 21b, the posteromedial lateral suprasylvian area and the ventral lateral suprasylvian area. The most medial zone, the intermediate division of the lateral posterior complex, projects to at least four cortical areas: 20a, the posterior suprasylvian area, the posterolateral lateral suprasylvian area and the dorsal lateral suprasylvian area. Of the 15 cortical areas that receive fibers from the pulvinar-lateral posterior complex, only three (areas 19, 20a and 21a) receive projections from more than one of these thalamic zones, and only one of the cortical areas (20a) receives fibers from all three zones. Thus, the data support the division of the pulvinar lateral posterior complex into three zones on the basis of their unique and largely non-overlapping projections to the visual cortex.