Evidence concerning anatomical connectivities in the human brain is sparse and based largely on limited post-mortem observations. Diffusion tensor imaging has previously been used to define large white-matter tracts in the living human brain, but this technique has had limited success in tracing pathways into gray matter. Here we identified specific connections between human thalamus and cortex using a novel probabilistic tractography algorithm with diffusion imaging data. Classification of thalamic gray matter based on cortical connectivity patterns revealed distinct subregions whose locations correspond to nuclei described previously in histological studies. The connections that we found between thalamus and cortex were similar to those reported for non-human primates and were reproducible between individuals. Our results provide the first quantitative demonstration of reliable inference of anatomical connectivity between human gray matter structures using diffusion data and the first connectivity-based segmentation of gray matter.

Non-invasive mapping of connections between human thalamus and cortex using diffusion imaging

During the past 100 years clinical studies of amnesia have linked memory impairment to damage of the hippocampus. Yet the damage in these cases has not usually been confined to the hippocampus, and the status of memory functions has often been based on incomplete neuropsychological information. Thus, the human cases have until now left some uncertainty as to whether lesions limited to the hippocampus are sufficient to cause amnesia. Here we report a case of amnesia in a patient (R.B.) who developed memory impairment following an ischemic episode. During the 5 years until his death, R.B. exhibited marked anterograde amnesia, little if any retrograde amnesia, and showed no signs of cognitive impairment other than memory. Thorough histological examination revealed a circumscribed bilateral lesion involving the entire CA1 field of the hippocampus. Minor pathology was found elsewhere in the brain (e.g., left globus pallidus, right postcentral gyrus, left internal capsule), but the only damage that could be reasonably associated with the memory defect was the lesion in the hippocampus. To our knowledge, this is the first reported case of amnesia following a lesion limited to the hippocampus in which extensive neuropsychological and neuropathological analyses have been carried out.

https://www.jneurosci.org/content/jneuro/6/10/2950.full.pdf

Human amnesia and the medial temporal region: enduring memory impairment following a bilateral lesion limited to field CA1 of the hippocampus

Dual functional brain asymmetry refers to the notion that in most individuals the left cerebral hemisphere is specialized for language functions, whereas the right cerebral hemisphere is more important than the left for the perception, construction, and recall of stimuli that are difficult to verbalize. In the last twenty years there have been scattered reports of sex differences in degree of hemispheric specialization. This review provides a critical framework within which two related topics are discussed: Do meaningful sex differences in verbal or spatial cerebral lateralization exist? and, if so, Is the brain of one sex more symmetrically organized than the other? Data gathered on right-handed adults are examined from clinical studies of patients with unilateral brain lesions; from dichotic listening, tachistoscopic, and sensorimotor studies of functional asymmetries in non-brain-damaged subjects; from anatomical and electrophysiological investigations, as well as from the developmental literature. Retrospective and descriptive findings predominate over prospective and experimental methodologies. Nevertheless, there is an impressive accummulation of evidence suggesting that the male brain may be more asymmetrically organized than the female brain, both for verbal and nonverbal functions. These trends are rarely found in childhood but are often significant in the mature organism.

Sex differences in human brain asymmetry: a critical survey

✓ The localization of cortical sites essential for language was assessed by stimulation mapping in the left, dominant hemispheres of 117 patients. Sites were related to language when stimulation at a current below the threshold for afterdischarge evoked repeated statistically significant errors in object naming. The language center was highly localized in many patients to form several mosaics of 1 to 2 sq cm, usually one in the frontal and one or more in the temporoparietal lobe. The area of individual mosaics, and the total area related to language was usually much smaller than the traditional Broca-Wernicke areas. There was substantial individual variability in the exact location of language function, some of which correlated with the patient's sex and verbal intelligence. These features were present for patients as young as 4 years and as old as 80 years, and for those with lesions acquired in early life or adulthood. These findings indicate a need for revision of the classical model of language locali...

Cortical language localization in left, dominant hemisphere. An electrical stimulation mapping investigation in 117 patients.

A model is proposed for integrating the neural and cognitive aspects of the positive symptoms of acute schizophrenia, using evidence from postmortem neuropathology and neurochemistry, clinical and preclinical studies of dopaminergic neurotransmission, anatomical connections between the limbic system and basal ganglia, attentional and other cognitive abnormalities underlying the positive symptoms of schizophrenia, specific animal models of some of these abnormalities, and previous attempts to model the cognitive functions of the septohippocampal system and the motor functions of the basal ganglia Anatomically, the model emphasises the projections from the septohippocampal system, via the subiculum, and the amygdala to nucleus accumbens, and their interaction with the ascending dopaminergic projection to the accumbens Psychologically, the model emphasises a failure in acute schizophrenia to integrate stored memories of past regularities of perceptual input with ongoing motor programs in the control of current perception A number of recent experiments that offer support for the model are briefly described, including anatomical studies of limbic-striatal connections, studies in the rat of the effects of damage to these connections, and of the effects of amphetamine and neuroleptics, on the partial reinforcement extinction effect, latent inhibition and the Kamin blocking effect; and studies of the latter two phenomena in acute and chronic schizophrenics

The neuropsychology of schizophrenia.

Variations and Connections of the Human Thalamus

On the nature of the "absence" in centrencephalic epilepsy: a study of some behavioral, electroencephalographic and autonomic factors.

Anomia from pulvinar and subcortical parietal stimulation

Introduction In recent years it has become increasingly apparent that seizures characterized by curious visceral and psychical states and automatism associated with a predominantly temporal localization of electroencephalographic abnormality form a large proportion of clinical seizure problems. This has been reported to be as high as 75%. 1 As more evidence has accumulated, the problems associated with a sound understanding of its mechanism have vastly expanded. The present study consists in a series of observations of patients subject to attacks of this sort. An attempt has been made in a number of pentylenetetrazol (Metrazol)-induced seizures to record graphically as many clinical, autonomic and electroencephalographic phenomena as possible which are interrelated by the same time base. By this means it was hoped to discover correlates that might be useful in understanding the mechanism of the ictal features of temporal lobe epilepsy. Methods The material selected for the present study consisted of

J.M. Van Buren

Papers

Variations and Connections of the Human Thalamus

On the nature of the "absence" in centrencephalic epilepsy: a study of some behavioral, electroencephalographic and autonomic factors.

Anomia from pulvinar and subcortical parietal stimulation

A correlation of autonomic and EEG components in temporal lobe epilepsy.

The architecture of the optic radiation in the temporal lobe of man