Wide Receptive Fields Research Articles

The palmo-mental reflex. An electrophysiological study.

Repeated electric stimulation of the ulnar nerve fibers was applied at the wrist in 7 normal and 32 pathological subjects; the response reflexes were simultaneously recorded in the chin muscles and at the upper limb, on the flexor carpi ulnaris. Although it is possible to obtain two distinct polysynaptic reflexes by cutaneous stimulation of the limb, the palmo-mental reflex causes a unique response, the latency of which may diminish to 35 msec. This response occurs most often at the threshold which elicits a nociceptive reflex of the upper limb. The palmo-mental reflex is almost always bilateral for a unilateral stimulation and in numerous instances is characterized by a wide receptive field. These findings suggest that the palmo-mental reflex is an early event in a general nociceptive response. In the normal subject this fragment of a general response to a painful stimulus is highly suppressed as are the local reflexes by suprasegmental control. The palmo-mental reflex is liberated and augmented in the event of habitually bilateral lesions of the pyramidal tract or the extra-pyramidal formations.

Responses in the spino-reticulo-cerebellar pathway to stimulation of cutaneous mechanoreceptors.

1. Mechanoreceptors in the footpad and in the hairy skin of the cat's fore- and hindlimbs were stimulated adequately. Evoked activity was recorded extracellularly, using averaging techniques, from 149 cells of the lateral reticular nucleus, LRN, and from 40 axons of its major spinal afferent tract, the bVFRT of Lundberg and Oscarsson (1962). 2. For both LRN cells and bVFRT axons the responses usually consisted of rather complex patterns of excitation and inhibition. 3. The following features were common for LRN cells and bVFRT axons: a) Most units showed a convergence from different types of receptors in one limb. b) Most units displayed a wide receptive field, comprising often both fore- and hind hindlimbs. However, receptors in forelimb usually proved more effective than those in hind limb; hairy skin receptors were more effective in distal than in proximal parts of the limb. 4. Although the latency histograms for both excitatory and inhibitory responses to mechanical stimulation of forelimb pad receptors display wide distributions, early peaks occur in the latency range of 10–14 ms. Distinct excitatory and inhibitory responses were observed as early as 8 ms. 5. Responses from mechanoreceptors were found to be much weaker in normal cats under nitrous oxide anaesthesia than in decerebrabe cats with the pyramidal tracts spared. This suggests an important control via descending pathways of the peripheral afferent input to the spino-reticulo-cerebellar paths.

Retinal projection in the forebrain of Emys orbicularis.

The latency and amplitude of evoked potentials in the general cortex of the turtle forebrain depend on localization of a point light source in the visual field. Maximal evoked responses show that retinal quadrants are connected predominantly with corresponding areas of the forebrain cortex. Most neurons (70 or 80) have wide receptive fields commensurate with the entire visual field. Distribution of the most effective points within the receptive field of the neurons also indicates their predominant connection with certain retinal quadrants. All dorsal cortical neurons exhibit high reactivity to displacement of objects in the visual field. A stationary light source also evokes different unit responses in the surface and deep layers of the cortex.

Somatotopic organization and response properties of neurons of the ventrobasal complex in the opossum.

AbstractThalamic responses to somatic stimulation were studied in 47 specimens of the South American opossum, D. marsupialis aurita. Topographic representation of the body surface in the ventrobasal complex was determined by recording unit cluster responses to natural stimulation in sodium pentobarbital anesthetised animals. The pattern of representation observed was similar to that reported in the North American subspecies and comparable to the findings in eutherian mammals.The analysis of single units recorded with extra‐cellular microelectrodes showed that the great majority of neurons are place and modality specific. A predominance of skin (vs. deep) sensibility was observed. Units activated by displacement of hairs and vibrissae displayed receptive fields similar to those reported in higher mammals. Of the units isolated within the anatomical boundaries of the ventrobasal complex only 1% showed wide receptive fields, or bilateral representation. None of the units could be activated by auditory stimulation. Neurons displaying wide, discontinuous or bilateral receptive fields showing auditory‐somatic convergence were isolated in nucleus parafascicularis, subparafascicularis and in the Posterior group.

Movement discrimination by the visual system of flies

1. A glass microelectrode was inserted into the optic lobes of fleshflies (Boettcherisca peregrina) and discharges responding to the movement of a spot of light were recorded. 2. Units responding to moving spot were classified into four types: non-directional, one directional, semi-integrative and integrative types. In addition, there was an “alerting” unit which discharged phasically to movement of a spot in any direction and adapted quickly, and an “inhibitory” unit in which discharges were inhibited by movement of a spot in any direction although a preferred direction was seen slightly. 3. Units of the non-directional type with relatively narrow receptive fields were found in the medulla only, while those with wide fields were in the lobula and the pathway to the central brain. 4. Units of the one directional type, which discharge to a preferred direction, were found in the region of the medulla to the lobula regardless of the size of the receptive field. 5. Units of the semi-integrative type, which possess a receptive field apparently formed by the combination of two or more fields of the one directional type and sometimes discharge dominantly to vertical movement at the front along the head axis, were found in all regions of the medulla to such central parts as the optic peduncle. 6. Units of the integrative type, which respond to such complex, but continuous movement as a circular motion of objects, were found in the central region from the lobula to the pathways to the brain. 7. Four types of relationships were found between the speed of the moving spot and the discharge rate: a, the discharge rate increased proportionally to the logarithm of the increase of the speed; b, the discharge rate was not altered by the speed changes; c, the discharge rate became maximal at a particular speed; d, the discharge rate was decreased or inhibited with increase of the speed. Type a was mainly seen in units of the one directional type with a wide receptive field and in units of the semi-integrative type, and was distributed over the region from the medulla to the lobula. Type b was found in units of the non-directional type with a narrow receptive field, and was situated in the medulla only. Type c was related with units of the directional and integrative types, and located in the central region of the optic lobes. Type d, seen in only few number, was found in the pathway to the central brain. 8. Orderly arrangement of the units, which suggests a neural mechanism for directional selectivity, was electrophysiologically observed. 9. It is concluded that the analytical processing of the direction and speed of movement is conducted in the region of the medulla to the lobula, and that the neural integration is performed in the central part of the optic lobes, the lobula and the pathway to the central brain.

Neuronal activity evoked in cat precruciate cerebral cortex by cutaneous stimulation

Extracellular recordings were made of the evoked activity of neurons in the precruciate forepaw cortex of the domestic cat after cutaneous stimulation of each limb. Neurons were classified according to the size of their excitatory receptive fields and whether or not their axons traversed the medullary pyramids. Neurons having bilateral receptive fields confined to the forelimbs and thoracic trunk region comprised 25% of the sample of 690 neurons; by contrast, only 6% of 1020 neurons from postcruciate arm cortex (gathered in a previous study) showed such fields. These neurons discharged with a short latency after stimulation of precruciate arm cortex of the opposite hemisphere; most other wide-field neurons but few small-field neurons responded to such interhemispheric activation. Many of the wide-field neurons responded to light or sound stimulation, or both, whereas few of the small-field neurons, including those with bilateral fields confined to the forelimb region, responded to such stimulation. Many wide-field neurons responded both to light touch and to hair-bending. Most pyramidal tract neurons had wide receptive fields. We concluded that the corticofugal elements in precruciate tissue receive information from cutaneous receptors of various types, distributed widely over the body surface, and that many of these elements are influenced by several modalities of sensory input. The “interneurons” of precruciate cortex, on the other hand, have sharply restricted input channels, and provide the most immediate and powerful modulation of corticofugal elements.

Termination and functional organization of the dorsal spino-olivocerebellar path.

1. The spino-olivocerebellar path ascending through the dorsal funiculus (DF-SOCP) was investigated in decerebrate cats with the cord transected in the third cervical segment except for the dorsal funiculi. The climbing fibre responses evoked in Purkinje cells were studied by recording the mass activity at the cerebellar surface and by recording from single cells.2. The DF-SOCP forms a disynaptic path from the spinal cord to the cerebellar cortex as shown by latency measurements. Anatomical studies have recently demonstrated that the relays are in the rostral part of the dorsal funiculus nuclei and in the dorsal accessory olive.3. The DF-SOCP projects to sagittal zones in the pars intermedia and vermis of the anterior lobe. The somatotopical organization is predominantly transverse in the pars intermedia and predominantly longitudinal in the vermis.4. The olivary neurones in the DF-SOCP are activated by the flexor reflex afferents from wide receptive fields. The fields are restricted to one ipsilateral limb and the majority of the olivary neurones could be activated from all the nerves tested in this limb.5. Natural stimulation of receptors evoked excitation in about half of the olivary neurones investigated. This excitation was elicited by pressure against deep structures. Inhibitory effects were rarely observed.6. The dorsal and ventral spino-olivocerebellar paths are compared.

Differential activity among wide-field neurons of the cat postcruciate cerebral cortex

Extracullular recordings were made of the evoked activity of neurons in sensorimotor cortex of cat following cutaneous stimulation of each limb. Neurons responding only to stimulation of the somatotopically “on focus” limb (CFP) were classed as s and separated from those responding to stimulation of at least one additional limb; the latter “wide-field” neurons were classed as m. The ratio of m to s increased from “sensory” to “motor” recording sites. Analysis was focused on m neurons of the postcruciate recording site—here 80% of the pyramidal tract (PT) cells were m neurons. Both “fast” and “slow” PT cells were identified, the latter residing more superficially and firing later than the former. Despite the wide receptive fields of these cells, a unique pattern of PT activity develops in the cortex that is somatotopically related to the cutaneous site of stimulation. This pattern results from a facilitatory action of s neurons on the PT, m elements, particularly the “slow” PT cells. The PT response patterns following stimulation at any other site are remarkably similar and suggest a “coadunating” function either in thalamus or cortex itself. The non-PT, m elements behave in a similar manner. These results restore a measure of somatotopic organization to the wide-field neurons. However, consideration of the anatomical distribution of PT elements and the physiological data supports the hypothesis that the pyramidal-tract elements originating in the postcruciate cortex of the cat serve primarily in an excitability-modulating capacity.

Organization of the posterior dorsal thalamus of the hedgehog.

AbstractA study of the responsiveness of single neurons in the hedgehog thalamus to sensory stimulation was undertaken with the hypothesis that modality specific relay nuclei characteristic of the mammalian thalamus differentiate out of a pool of multisensory neurons. Support for this hypothesis was obtained in earlier investigations of the opossum thalamus. In some ways the hedgehog may be an even better representative of a primitive stage of thalamic development. For example, there is very little structural difference between the ventroposterior nucleus and the medial geniculate body. The results of the present microelectrode investigation showed that neither the ventroposterior nucleus nor the medial geniculate body was modality specific. Further, many neurons in the ventroposterior nucleus showed wide receptive fields characteristic of the posterior group of nuclei in cats. This finding of convergence of sensory input upon single neurons of the dorsal thalamus in a generalized mammalian type suggests that the specificity characteristic of higher mammals is a product of an evolutionary trend. Thus comparative neurology provides additional evidence that precise receptive fields must play an important role in behavioral adaptation.