Human Lobe Research Articles

Evolution of prefrontal cortex.

Subdivisions of the prefrontal cortex (PFC) evolved at different times. Agranular parts of the PFC emerged in early mammals, and rodents, primates, and other modern mammals share them by inheritance. These are limbic areas and include the agranular orbital cortex and agranular medial frontal cortex (areas 24, 32, and 25). Rodent research provides valuable insights into the structure, functions, and development of these shared areas, but it contributes less to parts of the PFC that are specific to primates, namely, the granular, isocortical PFC that dominates the frontal lobe in humans. The first granular PFC areas evolved either in early primates or in the last common ancestor of primates and tree shrews. Additional granular PFC areas emerged in the primate stem lineage, as represented by modern strepsirrhines. Other granular PFC areas evolved in simians, the group that includes apes, humans, and monkeys. In general, PFC accreted new areas along a roughly posterior to anterior trajectory during primate evolution. A major expansion of the granular PFC occurred in humans in concert with other association areas, with modifications of corticocortical connectivity and gene expression, although current evidence does not support the addition of a large number of new, human-specific PFC areas.

The Subcortical-Allocortical- Neocortical continuum for the Emergence and Morphological Heterogeneity of Pyramidal Neurons in the Human Brain.

Human cortical and subcortical areas integrate emotion, memory, and cognition when interpreting various environmental stimuli for the elaboration of complex, evolved social behaviors. Pyramidal neurons occur in developed phylogenetic areas advancing along with the allocortex to represent 70–85% of the neocortical gray matter. Here, we illustrate and discuss morphological features of heterogeneous spiny pyramidal neurons emerging from specific amygdaloid nuclei, in CA3 and CA1 hippocampal regions, and in neocortical layers II/III and V of the anterolateral temporal lobe in humans. Three-dimensional images of Golgi-impregnated neurons were obtained using an algorithm for the visualization of the cell body, dendritic length, branching pattern, and pleomorphic dendritic spines, which are specialized plastic postsynaptic units for most excitatory inputs. We demonstrate the emergence and development of human pyramidal neurons in the cortical and basomedial (but not the medial, MeA) nuclei of the amygdala with cells showing a triangular cell body shape, basal branched dendrites, and a short apical shaft with proximal ramifications as “pyramidal-like” neurons. Basomedial neurons also have a long and distally ramified apical dendrite not oriented to the pial surface. These neurons are at the beginning of the allocortex and the limbic lobe. “Pyramidal-like” to “classic” pyramidal neurons with laminar organization advance from the CA3 to the CA1 hippocampal regions. These cells have basal and apical dendrites with specific receptive synaptic domains and several spines. Neocortical pyramidal neurons in layers II/III and V display heterogeneous dendritic branching patterns adapted to the space available and the afferent inputs of each brain area. Dendritic spines vary in their distribution, density, shapes, and sizes (classified as stubby/wide, thin, mushroom-like, ramified, transitional forms, “atypical” or complex forms, such as thorny excrescences in the MeA and CA3 hippocampal region). Spines were found isolated or intermingled, with evident particularities (e.g., an extraordinary density in long, deep CA1 pyramidal neurons), and some showing a spinule. We describe spiny pyramidal neurons considerably improving the connectional and processing complexity of the brain circuits. On the other hand, these cells have some vulnerabilities, as found in neurodegenerative Alzheimer’s disease and in temporal lobe epilepsy.

Survival of retinal ganglion cells after damage to the occipital lobe in humans is activity-dependent

Damage to the optic radiations or primary visual cortex leads to blindness in all or part of the contralesional visual field. Such damage disconnects the retina from its downstream targets and, ove...

Survival of retinal ganglion cells after damage to the occipital lobe in humans is activity dependent.

Damage to the optic radiations or primary visual cortex leads to blindness in all or part of the contralesional visual field. Such damage disconnects the retina from its downstream targets and, over time, leads to trans-synaptic retrograde degeneration of retinal ganglion cells. To date, visual ability is the only predictor of retinal ganglion cell degeneration that has been investigated after geniculostriate damage. Given prior findings that some patients have preserved visual cortex activity for stimuli presented in their blind field, we tested whether that activity explains variability in retinal ganglion cell degeneration over and above visual ability. We prospectively studied 15 patients (four females, mean age = 63.7 years) with homonymous visual field defects secondary to stroke, 10 of whom were tested within the first two months after stroke. Each patient completed automated Humphrey visual field testing, retinotopic mapping with functional magnetic resonance imaging, and spectral-domain optical coherence tomography of the macula. There was a positive relation between ganglion cell complex (GCC) thickness in the blind field and early visual cortex activity for stimuli presented in the blind field. Furthermore, residual visual cortex activity for stimuli presented in the blind field soon after the stroke predicted the degree of retinal GCC thinning six months later. These findings indicate that retinal ganglion cell survival after ischaemic damage to the geniculostriate pathway is activity dependent.

The Lateral Temporal Lobe in Early Human Life.

Abnormalities of lateral temporal lobe development are associated with a spectrum of genetic and environmental pathologic processes, but more normative data are needed for a better understanding of gyrification in this brain region. Here, we begin to establish guidelines for the analysis of the lateral temporal lobe in humans in early life. We present quantitative methods for measuring gyrification at autopsy using photographs of the gross brain and simple computer-based quantitative tools in a cohort of 28 brains ranging in age from 27 to 70 postconceptional weeks (end of infancy). We provide normative ranges for different indices of gyrification and identify a constellation of qualitative features that should also be considered in these analyses. The ratio of the temporal area to the whole brain area increased dramatically in the second half of gestation, but then decelerated after birth before increasing linearly around 50 postconceptional weeks. Tertiary gyrification continued beyond birth in a linear process through infancy with considerable variation in patterns. Analysis of 2 brains with gyral disorders of the lateral temporal lobe demonstrated proof-of-principle that the proposed methods are of diagnostic value. These guidelines are proposed for assessments of temporal lobe pathology in pediatric brains in early life.

Brodmann Areas 27, 28, 36 and 37: The Parahippocampal and the Fusiform Gyri

First, Brodmann areas 27, 28, 36 and 37, were anatomically defined in the beginning of this review. These areas exist in the parahippocampal or fusiform gyrus of the ventral temporal lobe in humans. Subsequently, the current understanding of their functions was summarized on the basis of recent findings mainly through human functional neuroimaging studies and animal studies. Rodent studies have shown the existence of neuronal activities for representing space, such as those involving head-direction cells or grid cells, in areas 27 (the parasubicular cortex) and 28 (the ventral entorhinal cortex). Recent human neuroimaging studies have provided support for the idea that grid cells may also exist in the human entorhinal cortex. Many previous animal studies have shown that area 36 (the lateral perirhinal cortex) is crucial for various types of associative learning. Earlier human neuroimaging studies have also indicated that faces, bodies and visual word forms are represented in different regions of area 37 in the posterior fusiform gyrus. Recent neuroimaging studies in humans have shown substantial functional differentiation between face-related regions in areas 37 and 36, which is similar to that seen in macaque monkeys, as shown through their face patches. This implies the crucial involvement of both areas in face processing.

The implications of brain lateralisation for modern general practice.

Anatomy of the Brain. 1802. From: The Anatomy of the Brain Explained in a Series of Engravings, by Sir Charles Bell. Credit: Wellcome Library, London. Iain McGilchrist, an Oxford literary scholar turned psychiatrist, recently published The Master and His Emissary: The Divided Brain And The Making of The Western World .1 His thesis, based on an extensive review and synthesis of the neuroscientific, philosophical, and humanities literature, is that there are two fundamentally opposed realities, different modes of experience, which contribute to how humans understand the world. These differences are rooted in the bi-hemispheric structure of the brain and although the hemispheres are functionally integrated on a day-to-day basis, their different priorities are likely to come into conflict in the long term. He hypothesises that this conflict explains many aspects of contemporary Western culture and I believe McGilchrist’s thesis sheds light on many of the issues we find ourselves now facing in general practice. Lateralisation of brain function is widespread in vertebrates.2 Birds and mammals developed bi-hemispheric brains, which brought evolutionary advantages through being able to perform cognitive tasks that demand simultaneous, but different, use of both hemispheres, for example, finding food while being vigilant for predators.3 The advantages accrue not only at individual but also at population level, where lateralisation produces advantages in social cohesion, for example, by being able to relate to others as a potential mate or friend. As the brain evolved, the cerebral hemispheres increased in size. The expansion of the frontal lobes in humans has allowed us …

Cerebral Networks of Interfacial Water: Analogues of the Neural Correlates of Consciousness in a Synthetic Three-Shell Realistic Head Model

The physical properties of water, particularly the nature of interfacial water and pH shifts associated with dynamics of the hydronium ion near any surface, may be a primary source of the complex electromagnetic patterns frequently correlated with consciousness. Effectively all of the major correlates of consciousness, including the 40 Hz and 8 Hz coupling between the cerebral cortices and hippocampal formation, can be accommodated by the properties of water within a specific-shaped volume exposed to a magnetic field. In the present study, quantitative electroencephalographic activity was measured from an experimental simulation of the human head constructed using conductive dough whose pH could be changed systematically. Spectral analyses of electrical potentials generated over the regions equivalent to the left and right temporal lobes in humans exhibited patterns characteristic of Schumann Resonance. This fundamental and its harmonics are generated within the earth-ionospheric cavity with intensities similar to the volumetric intracerebral magnetic (~2 pT) and electric field (~6 × 10-1 V·m-1) strengths. The power densities for specific pH values were moderately correlated with those obtained from normal human brains for the fundamental (first) and second harmonic for the level simulating the cerebral cortices. Calculations indicated that the effective pH would be similar to that encountered within a single layer of protons near the plasma membrane surface. These results reiterate recent measurements in a large population of human brains showing the superimposition of Schumann power densities in QEEG data and indicate that intrinsic features of proton densities within cerebral water may be a fundamental basis to consciousness that can be simulated experimentally.

Impairments of executive functions

Event Abstract Back to Event Impairments of executive functions Guy Vingerhoets1* 1 Ghent University, Experimental Psychology, Belgium Compared to other primate and non-primate mammals, the enlargement of the frontal lobe in humans is striking. Given the recent expansion of this region in our species over the course of the evolution, it comes as no surprise that the frontal lobes have been strongly associated with particular human qualities such as the production of language, fine manual dexterity and tool use, consciousness, memory, and the planning and control of goal-directed behavior. Given the frontal lobes’ location and size, this part of the brain appears vulnerable to damage. Head trauma, cerebrovascular disease, and brain tumors are the most common causes of frontal lobe damage, but neurodegenerative diseases and psychiatric disorders are also frequently associated with frontal dysfunction. Many patients suffering frontal lobe impairment show a loss of control over basic cognitive functions characterized as impairments of initiation, planning, sequencing, inhibition, flexibility and monitoring, and this behavioral profile is often described as the ‘dysexecutive syndrome’. Clearly, not all patients with frontal lesions exhibit the full spectrum of executive difficulties and evidence is accumulating that we should differentiate several functional domains that can be selectively damaged following focal frontal damage. The existence of distinct functional domains within the frontal lobe is supported by anatomical evidence, neuroimaging and lesion studies, although it remains difficult to assess some of these domains with the available clinical tools. Improved diagnostic precision may give rise to tailored intervention, and we will discuss some of the possible behavioral approaches to the rehabilitation of executive functioning. Keywords: Dysexecutive Syndrome, Frontal Lobe, executive functions, Neuropsychological Tests, Rehabilitation Conference: Belgian Brain Council, Liège, Belgium, 27 Oct - 27 Oct, 2012. Presentation Type: Oral Presentation (only for invited speakers) Topic: Higher Brain Functions in health and disease: cognition and memory Citation: Vingerhoets G (2012). Impairments of executive functions. Conference Abstract: Belgian Brain Council. doi: 10.3389/conf.fnhum.2012.210.00066 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 04 Sep 2012; Published Online: 12 Sep 2012. * Correspondence: Prof. Guy Vingerhoets, Ghent University, Experimental Psychology, Ghent, B-9000, Belgium, guy.vingerhoets@ugent.be Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Guy Vingerhoets Google Guy Vingerhoets Google Scholar Guy Vingerhoets PubMed Guy Vingerhoets Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Poststroke Conscious Visual Deficit

Background and Purpose. Little is known about the outcome and recovery mechanisms of visual perception after a focal lesion of the occipital lobe in humans, especially after stroke. In this study, the authors aimed to describe the clinical course and the neural substrates of conscious perceptive visual deficit after posterior cerebral artery infarct. Methods. The authors prospectively included 8 patients (7 men and 1 woman; mean age, 64.6 ± 18 years) with visual deficit induced by partial damage of the striate cortex related to acute posterior cerebral artery infarct. Conscious perception of color and motion was assessed from the acute phase to the third month. Functional magnetic resonance imaging was performed to investigate neural substrates of visual recovery. Results. In the acute phase of stroke, visual deficiency was global (3/8 patients), selective to color (4/8 patients), or selective to motion (1/8 patients). During the follow-up, visual performance increased with respect to color (from 29% to 70%; P < .005) and with respect to motion (from 47% to 74%; P < .005). Despite a lack of ipsilesional V1 area activation in the acute phase, activations in this area and in the contralesional extrastriate cortex were obtained during follow-up. Both ipsilesional and contralesional V4 activations were correlated with better outcome. Conclusions. Extensive visual recovery occurs early after partial acute posterior cerebral artery infarct. Spared islands in ipsilesional V1 area and transcallosal pathways might be involved in poststroke visual recovery.

Improvements in high‐field localized MRS of the medial temporal lobe in humans using new deformable high‐dielectric materials

The intrinsic nonuniformities in the transmit radiofrequency field from standard quadrature volume resonators at high field are particularly problematic for localized MRS in areas such as the temporal lobe, where a low signal-to-noise ratio and poor metabolite quantification result from destructive B₁⁺ field interference, in addition to line broadening and signal loss from strong susceptibility gradients. MRS of the temporal lobe has been performed in a number of neurodegenerative diseases at clinical fields, but a relatively low signal-to-noise ratio has prevented the reliable quantification of, for example, glutamate and glutamine, which are thought to play a key role in disease progression. Using a recently developed high-dielectric-constant material placed around the head, localized MRS of the medial temporal lobe using the stimulated echo acquisition mode sequence was acquired at 7 T. The presence of the material increased the signal-to-noise ratio of MRS by a factor of two without significantly reducing the sensitivity in other areas of the brain, as shown by the measured B₁⁺ maps. An increase in the receive sensitivity B₁⁻ was also measured close to the pads. The spectral linewidth of the unsuppressed water peak within the voxel of interest was reduced slightly by the introduction of the dielectric pads (although not to a statistically significant degree), a result confirmed by using a pad composed of lipid. Using LCmodel for quantitative analysis of metabolite concentrations, the increase in signal-to-noise ratio and the slight decrease in spectral linewidth contributed to statistically significant reductions in the Cramer-Rao lower bounds (CRLBs), also allowing the levels of glutamate and glutamine to be quantified with CRLBs below 20%.

Genetic malformations of the human frontal lobe.

Interest in genetic malformations of the frontal lobe has grown from the recognition that certain brain malformations have a predilection for the frontal lobes or are more severe in the anterior brain. These malformations can be deleterious, as the frontal lobes in humans are particularly large in comparison with those of other species and play an important role in cognitive developmental functions.

Painful stimuli evoke potentials recorded from the medial temporal lobe in humans

The role of human medial temporal structures in fear conditioning has led to the suggestion that neurons in these structures might respond to painful stimuli. We have now tested the hypothesis that recordings from these structures will demonstrate potentials related to the selective activation of cutaneous nociceptors by a painful laser stimulus (laser evoked potential, LEP) (Kenton B, Coger R, Crue B, Pinsky J, Friedman Y, Carmon A (1980) Neurosci Lett 17:301–306). Recordings were carried out through electrodes implanted bilaterally in these structures for the investigation of intractable epilepsy. Reproducible LEPs were commonly recorded both bilaterally and unilaterally, while LEPs were recorded at contacts on the left (9/14, P=0.257) as commonly as on the right (5/14), independent of the hand stimulated. Along electrodes traversing the amygdala the majority of LEPs were recorded from dorsal contacts near the central nucleus of the amygdala and the nucleus basalis. Stimulus evoked changes in theta activity were observed at contacts on the right at which isolated early negative LEPs (N2*) responses could be recorded. Contacts at which LEPs could be recorded were as commonly located in medial temporal structures with evidence of seizure activity as on those without. These results demonstrate the presence of pain-related inputs to the medial temporal lobe where they may be involved in associative learning to produce anxiety and disability related to painful stimuli.

Ultra-Rapid Sensory Responses in the Human Frontal Eye Field Region

Most of what we know about the human frontal eye field (FEF) is extrapolated from studies in animals. There is ample evidence that this region is crucial for eye movements. However, evidence is accumulating that this region also plays a role in sensory processing and that it belongs to a "fast brain" system. We set out to investigate these issues in humans, using intracerebral recordings in patients with drug-refractory epilepsy. Event-related potential recordings were obtained from 11 epileptic patients from within the FEF region while they passed a series of visual and auditory perceptual tests. No eye movement was required. Ultra-rapid responses were observed, with mean onset latencies at 24 ms after stimulus to auditory stimuli and 45 ms to visual stimuli. Such early responses were compatible with cortical routes as assessed with simultaneous recordings in primary auditory and visual cortices. Components were modulated very early by the sensory characteristics of the stimuli, in the 30-60 ms period for auditory stimuli and in the 45-60 ms period for visual stimuli. Although the frontal lobes in humans are generally viewed as being involved in high-level cognitive processes, these results indicate that the human FEF is a remarkably quickly activated multimodal region that belongs to a network of low-level neocortical sensory areas.

MRI diffusion tensor tracking of a new amygdalo‐fusiform and hippocampo‐fusiform pathway system in humans

To use MRI diffusion-tensor tracking (DTT) to test for the presence of unknown neuronal fiber pathways interconnecting the mid-fusiform cortex and anteromedial temporal lobe in humans. Such pathways are hypothesized to exist because these regions coactivate in functional MRI (fMRI) studies of emotion-valued faces and words, suggesting a functional link that could be mediated by neuronal connections. A total of 15 normal human subjects were studied using unbiased DTT approaches designed for probing unknown pathways, including whole-brain seeding and large pathway-selection volumes. Several quality-control steps verified the results. Parallel amygdalo-fusiform and hippocampo-fusiform pathways were found in all subjects. The pathways begin/end at the mid-fusiform gyrus above the lateral occipitotemporal sulcus bilaterally. The superior pathway ends/begins at the superolateral amygdala. The inferior pathway crosses medially and ends/begins at the hippocampal head. The pathways are left-lateralized, with consistently larger cross-sectional area, higher anisotropy, and lower minimum eigenvalue (D-min) on the left, where D-min assesses intrinsic cross-fiber diffusivity independent of curvature. A previously-undescribed pathway system interconnecting the mid-fusiform region with the amygdala/hippocampus has been revealed. This pathway system may be important for recognition, memory consolidation, and emotional modulation of face, object, and lexical information, which may be disrupted in conditions such as Alzheimer's disease.

Perception and production of emotional speech in Parkinson's disease

not received. CS3.5 Functional connectivity of the mesial temporal lobe in humans: an electrical study

Functional connectivity of the mesial temporal lobe in humans: an electrical study

Functional connectivity of the mesial temporal lobe in humans: an electrical study

Characterizing interneuron and pyramidal cells in the human medial temporal lobe in vivo using extracellular recordings

The goal of this study was to characterize the electrophysiological features of single neurons recorded deep within the medial temporal lobes in humans. Using three physiological criteria to distinguish principal cells and interneurons (firing rate, burst propensity, and action potential waveform) and a large data set of human single neurons (585) from thirteen patients, we show that single neurons in the human MTL separate into two distinct classes comparable to the pyramidal cell and interneuron classes described in animals. We also find that the four different MTL brain regions that we examined (amygdala, hippocampus, entorhinal cortex, and posterior parahippocampal cortex) show unique action potential characteristics, which may in turn relate to the role that neurons from these regions play in behavior. A subset of cells were recorded while patients engaged in both slow-wave (SWS) and rapid-eye movement (REM) sleep and a comparison of the electrophysiological features during these different sleep stages showed that interneurons tended to burst more during SWS compared to REM, while only principal cells in the EC and hippocampus showed a greater propensity for bursting during SWS. Together, our results support the idea that human single neurons have electrophysiologically identifiable cell types, similar to those observed in other mammals, and provide insight into regional and functional differences in spike-wave characteristics relevant to considerations about neural populations in the human brain.

Automatic affective stimulus processing is intact after unilateral resection of the anterior temporal lobe in humans

Only hundreds of milliseconds after an incoming stimulus is perceived, we make an evaluation of whether it is good or bad. This evaluation seems to occur automatically and can significantly influence behavior. According to several functional imaging studies, the amygdala, which is localized in the temporal lobes of the brain, is an important structure for the automatic processing of affective stimuli. To investigate how critical a role the amygdala plays in this process, we had 20 participants with unilateral resection of the temporal lobe and 20 controls perform an affective priming task. Both controls and patients demonstrated shorter response latencies on trials where prime and target had the same valence than on trials where prime and target had the opposite valence. This finding is generally known as the affective priming effect and is considered to reflect automatic stimulus evaluation. More specifically, it is assumed that the valence of the prime stimulus is activated automatically and exerts an influence on the speed by which the target stimulus is evaluated. Given that the affective priming effect is equally large in both groups, our results suggest that the automatic processing of stimulus valence is intact in participants who sustained unilateral resection of the temporal lobe.

Evaluative conditioning is intact after unilateral resection of the anterior temporal lobe in humans

Several lesion and functional imaging studies conducted in animals and humans suggest that structures within the amygdaloid nuclear complex (ANC) are important for the occurrence of fear conditioning. Whether this brain structure is also critical for evaluative conditioning, has been investigated less frequently. In the current experiment, a group of participants with unilateral resection of the anterior temporal lobe and a control group received a differential evaluative flavor-taste conditioning task. In the pre-acquisition phase, two fruit flavors (the conditioned stimuli (CSs)) were presented and participants were instructed to evaluate both. In the subsequent acquisition phase, one of these fruit flavors (CS+) was presented together with a bad tasting substance Tween20 (polysorbate 20, the US), while the other flavor (CS−) was never paired with Tween20. Finally, in the post-acquisition phase, the two flavors were presented again without Tween20 and participants were asked to evaluate both of them for a last time. The control group as well as the lesion group rated the CS+ in the post-acquisition phase less favorable than in the pre-acquisition phase, while the ratings of the CS− remained the same in both phases. We clearly demonstrated evaluative conditioning in both test groups. Because the lesion group had still one intact ANC it would be premature, however, to conclude that the ANC is not involved in evaluative conditioning. We conclude that despite evidence for impaired fear conditioning, unilateral damage to the ANC does not impair evaluative conditioning.