Insular Cortical Projections to Functional Regions of the Striatum Correlate with Cortical Cytoarchitectonic Organization in the Primate

We examined the striatal projections from different cytoarchitectonic regions of the insular cortex using anterograde and retrograde techniques. The shell and medial ventral striatum receive inputs primarily from the agranular and ventral dysgranular insula. The central ventral striatum receives inputs primarily from the dorsal agranular and dysgranular insula. Projections to the central ventral striatum originate from more posterior and dorsal insular regions than projections to the medial ventral striatum. The dorsolateral striatum receives projections primarily from the dorsal dysgranular and granular insula.

These results show that cytoarchitectonically less differentiated (agranular) insular regions project to the ventromedial "limbic" part of the ventral striatum, whereas more differentiated (granular) insular regions project to the dorsolateral "sensorimotor" part of the striatum. The finding that the ventral "limbic" striatum receives inputs from less differentiated regions of the insula is consistent with the general principle that less differentiated cortical regions project primarily to the "limbic" striatum. Functionally, the ventral striatum receives insular projections primarily related to integrating feeding behavior with rewards and memory, whereas the dorsolateral striatum receives insular inputs related to the somatosensation. Information regarding food acquisition in the insula may be sent to the intermediate area of the striatum.

Masanori Chikama, Nikolaus R. McFarland, David G. Amaral, and Suzanne N. Haber
Insular Cortical Projections to Functional Regions of the Striatum Correlate with Cortical Cytoarchitectonic Organization in the Primate
J. Neurosci. 17: 9686-9705; doi:

http://www.jneurosci.org/cgi/content/full/17/24/9686

Changes in brain activity related to eating chocolate

We performed successive H215O-PET scans on volunteers as they ate chocolate to beyond satiety. Thus, the sensory stimulus and act (eating) were held constant while the reward value of the chocolate and motivation of the subject to eat were manipulated by feeding. Non-specific effects of satiety (such as feelings of fullness and autonomic changes) were also present and probably contributed to the modulation of brain activity. After eating each piece of chocolate, subjects gave ratings of how pleasant/unpleasant the chocolate was and of how much they did or did not want another piece of chocolate. Regional cerebral blood flow was then regressed against subjects' ratings. Different groups of structures were recruited selectively depending on whether subjects were eating chocolate when they were highly motivated to eat and rated the chocolate as very pleasant [subcallosal region, caudomedial orbitofrontal cortex (OFC), insula/operculum, striatum and midbrain] or whether they ate chocolate despite being satiated (parahippocampal gyrus, caudolateral OFC and prefrontal regions). As predicted, modulation was observed in cortical chemosensory areas, including the insula and caudomedial and caudolateral OFC, suggesting that the reward value of food is represented here. Of particular interest, the medial and lateral caudal OFC showed opposite patterns of activity. This pattern of activity indicates that there may be a functional segregation of the neural representation of reward and punishment within this region. The only brain region that was active during both positive and negative compared with neutral conditions was the posterior cingulate cortex. Therefore, these results support the hypothesis that there are two separate motivational systems: one orchestrating approach and another avoidance behaviours.

Dana M. Small , Robert J. Zatorre , Alain Dagher , Alan C. Evans , and Marilyn Jones-Gotman
Changes in brain activity related to eating chocolate: From pleasure to aversion
Brain 124: 1720-1733.

http://brain.oxfordjournals.org/cgi/content/full/124/9/1720

A Specific Role for the Thalamus in Mediating the Interaction of Attention and Arousal in Humans

The physiological basis for the interaction of selective attention and arousal is not clearly understood. Here we present evidence in humans that specifically implicates the thalamus in this interaction. We used functional magnetic resonance imaging to measure brain activity during the performance of an attentional task under different levels of arousal. Activity evoked in the ventrolateral thalamus by the attentional task changed as a function of arousal. The highest level of attention-related thalamic activity is seen under conditions of low arousal (secondary to sleep deprivation) compared with high arousal (secondary to caffeine administration). Other brain regions were also active during the attentional task, but these areas did not change their activity as a function of arousal. Control experiments establish that this pattern of changes in thalamic activity cannot be accounted for by nonspecific effects of arousal on cerebral hemodynamics. We conclude that the thalamus is involved in mediating the interaction of attention and arousal in humans.

C. M. Portas, G. Rees, A. M. Howseman, O. Josephs, R. Turner, and C. D. Frith
A Specific Role for the Thalamus in Mediating the Interaction of Attention and Arousal in Humans
J. Neurosci. 18: 8979-8989; doi:

http://www.jneurosci.org/cgi/content/full/18/21/8979

The Connectional Organization of the Cortico-thalamic System of the Cat

Data on connections between the areas of the cerebral cortex and nuclei of the thalamus are too complicated to analyse with naked intuition. Indeed, the complexity of connection data is one of the major challenges facing neuroanatomy. Recently, systematic methods have been developed and applied to the analysis of the connectivity in the cerebral cortex. These approaches have shed light on the gross organization of the cortical network, have made it possible to test systematically theories of cortical organization, and have guided new electrophysiological studies. This paper extends the approach to investigate the organization of the entire corticothalamic network. An extensive collation of connection tracing studies revealed ~1500 extrinsic connections between the cortical areas and thalamic nuclei of the cat cerebral hemisphere. Around 850 connections linked 53 cortical areas with each other, and around 650 connections linked the cortical areas with 42 thalamic nuclei. Non-metric multidimensional scaling, optimal set analysis and non-parametric cluster analysis were used to study global connectivity and the `place' of individual structures within the overall scheme. Thalamic nuclei and cortical areas were in intimate connectional association. Connectivity defined four major thalamocortical systems. These included three broadly hierarchical sensory or sensory/motor systems (visual and auditory systems and a single system containing both somatosensory and motor structures). The highest stations of these sensory/motor systems were associated with a fourth processing system composed of prefrontal, cingulate, insular and parahippocampal cortex and associated thalamic nuclei (the `fronto-limbic system'). The association between fronto-limbic and somato-motor systems was particularly close.

J.W. Scannell , G.A.P.C. Burns , C.C. Hilgetag , M.A. O'Neil , and M.P. Young
The Connectional Organization of the Cortico-thalamic System of the Cat
Cereb. Cortex 9: 277-299.

http://cercor.oxfordjournals.org/cgi/content/full/9/3/277

Pathways for emotions and memory I. Input and output zones linking the anterior thalamic nuclei with prefrontal cortices in the rhesus monkey

The anterior thalamic nuclei occupy a central position in pathways associated with emotions and memory. The goal of this study was to determine the anatomic interaction of the anterior nuclei with distinct prefrontal cortices that have been implicated in emotion and specific aspects of memory. To address this issue, we investigated the relationship of input and output zones in the anterior thalamic nuclei linking them with functionally distinct orbitofrontal, medial, and lateral prefrontal cortices. We identified input zones by mapping the pattern and topography of terminations of prefrontal axons, and the output zones by mapping projection neurons in the anterior nuclei, after injection of anterograde and bidirectional tracers in distinct prefrontal cortices. The results showed that the anterior nuclei were preferentially connected with some orbitofrontal and medial prefrontal areas. In contrast, the anterior nuclei had comparatively sparse connections with most lateral prefrontal cortices, with the notable exception of frontal polar cortex, which had moderate but consistent connections with the anterior nuclei. Prefrontal cortices were connected mostly with the anterior medial nucleus, though medial areas 32 and 25 as well as the frontal polar cortex were also connected with the anterior ventral nucleus.
The zones of axonal terminations were more expansive than the sites with projection neurons in the anterior nuclei, suggesting extensive influence of feedback projections from prefrontal cortices. The results suggest that the anterior thalamic nuclei may act in concert with
orbitofrontal and medial prefrontal cortices in processes underlying emotions and long-term memory, and with the frontal polar cortex in prospective aspects of working memory.


D. Xiao, H. Barbas
Pathways for emotions and memory I. Input and output zones linking the anterior thalamic nuclei with prefrontal cortices in the rhesus monkey
Thalamus & Related Systems 2 (2002) 21–32

http://www.bu.edu/neural/Final/Publications/2002/Thalamus%20&%20Related%20Systems,%20Volume%202,%20Issue%201,%20December%202002,%20Pages%2021-32.pdf

Involvement of the Superior Temporal Cortex and the Occipital Cortex in Spatial Hearing: Evidence from Repetitive Transcranial Magnetic Stimulation

The processing of auditory spatial information in cortical areas of the human brain outside of the primary auditory cortex remains poorly understood. Here we investigated the role of the superior temporal gyrus (STG) and the occipital cortex (OC) in spatial hearing using repetitive transcranial magnetic stimulation (rTMS). The right STG is known to be of crucial importance for visual spatial awareness, and has been suggested to be involved in auditory spatial perception. We found that rTMS of the right STG induced a systematic error in the perception of interaural time differences (a primary cue for sound localization in the azimuthal plane). This is in accordance with the recent view, based on both neurophysiological data obtained in monkeys and human neuroimaging studies, that information on sound location is processed within a dorsolateral "where" stream including the caudal STG. A similar, but opposite, auditory shift was obtained after rTMS of secondary visual areas of the right OC. Processing of auditory information in the OC has previously been shown to exist only in blind persons. Thus, the latter finding provides the first evidence of an involvement of the visual cortex in spatial hearing in sighted human subjects, and suggests a close interconnection of the neural representation of auditory and visual space. Because rTMS induced systematic shifts in auditory lateralization, but not a general deterioration, we propose that rTMS of STG or OC specifically affected neuronal circuits transforming auditory spatial coordinates in order to maintain alignment with vision.

Lewald, Jorg, Meister, Ingo G., Weidemann, Jurgen, Topper, Rudolf
Involvement of the Superior Temporal Cortex and the Occipital Cortex in Spatial Hearing: Evidence from Repetitive Transcranial Magnetic Stimulation
J. Cogn. Neurosci. 2004 16: 828-838

http://jocn.mitpress.org/cgi/citmgr?gca=jocn;16/5/828

Social concepts are represented in the superior anterior temporal cortex

Social concepts such as "tactless" or "honorable" enable us to describe our own as well as others' social behaviors. The prevailing view is that this abstract social semantic knowledge is mainly subserved by the same medial prefrontal regions that are considered essential for mental state attribution and self-reflection. Nevertheless, neurodegeneration of the anterior temporal cortex typically leads to impairments of social behavior as well as general conceptual knowledge. By using functional MRI, we demonstrate that the anterior temporal lobe represents abstract social semantic knowledge in agreement with this patient evidence. The bilateral superior anterior temporal lobes (Brodmann's area 38) are selectively activated when participants judge the meaning relatedness of social concepts (e.g., honor–brave) as compared with concepts describing general animal functions (e.g., nutritious–useful). Remarkably, only activity in the superior anterior temporal cortex, but not the medial prefrontal cortex, correlates with the richness of detail with which social concepts describe social behavior. Furthermore, this anterior temporal lobe activation is independent of emotional valence, whereas medial prefrontal regions show enhanced activation for positive social concepts. Our results demonstrate that the superior anterior temporal cortex plays a key role in social cognition by providing abstract conceptual knowledge of social behaviors. We further speculate that these abstract conceptual representations can be associated with different contexts of social actions and emotions through integration with frontolimbic circuits to enable flexible evaluations of social behavior.

Roland Zahn, Jorge Moll, Frank Krueger, Edward D. Huey, Griselda Garrido, and Jordan Grafman
Social concepts are represented in the superior anterior temporal cortex
Proceedings of the National Academy of Sciences 104: 6430-6435; published online before print as 10.1073/pnas.0607061104

http://www.pnas.org/cgi/content/full/104/15/6430