Co-Planar Stereotaxic Atlas of the Human Brain—3-Dimensional Proportional System: An Approach to Cerebral Imaging, J. Talairach, P. Tournoux. Georg Thieme Verlag, New York (1988), 122 pp., 130 figs. DM 268

Bartlett viewed thinking as a high level skill exhibiting ballistic properties that he called its “point of no return”. This paper explores one aspect of cognition through the use of a simple model...

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Orienting of attention

The two basic phenomena that define the problem of visual attention can be illustrated in a simple example. Consider the arrays shown in each panel of Figure 1. In a typical experiment, before the arrays were presented, subjects would be asked to report letters appearing in one color (targets, here black letters), and to disregard letters in the other color (nontargets, here white letters). The array would then be briefly flashed, and the subjects, without any opportunity for eye movements, would give their report. The display mimics our. usual cluttered visual environment: It contains one or more objects that are relevant to current behavior, along with others that are irrelevant. The first basic phenomenon is limited capacity for processing information. At any given time, only a small amount of the information available on the retina can be processed and used in the control of behavior. Subjectively, giving attention to any one target leaves less available for others. In Figure 1, the probability of reporting the target letter N is much lower with two accompa­ nying targets (Figure la) than with none (Figure Ib). The second basic phenomenon is selectivity-the ability to filter out un­ wanted information. Subjectively, one is aware of attended stimuli and largely unaware of unattended ones. Correspondingly, accuracy in identifying an attended stimulus may be independent of the number of nontargets in a display (Figure la vs Ie) (see Bundesen 1990, Duncan 1980).

Neural Mechanisms of Selective Visual Attention

: The concept of attention as central to human performance extends back to the start of experimental psychology, yet even a few years ago, it would not have been possible to outline in even a preliminary form a functional anatomy of the human attentional system. New developments in neuroscience have opened the study of higher cognition to physiological analysis, and have revealed a system of anatomical areas that appear to be basic to the selection of information for focal (conscious) processing. The importance of attention is its unique role in connecting the mental level of description of processes used in cognitive science with the anatomical level common in neuroscience. Sperry describes the central role that mental concepts play in understanding brain function. As is the case for sensory and motor systems of the brain, our knowledge of the anatomy of attention is incomplete. Nevertheless, we can now begin to identify some principles of organization that allow attention to function as a unified system for the control of mental processing. Although many of our points are still speculative and controversial, we believe they constitute a basis for more detailed studies of attention from a cognitive-neuroscience viewpoint. Perhaps even more important for furthering future studies, multiple methods of mental chronometry, brain lesions, electrophysiology, and several types of neuro-imaging have converged on common findings.

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The Attention System of the Human Brain

Attention deficit hyperactivity disorder (ADHD) comprises a deficit in behavioral inhibition. A theoretical model is constructed that links inhibition to 4 executive neuropsychological functions that appear to depend on it for their effective execution: (a) working memory, (b) self-regulation of affect-motivation-arousal, (c) internalization of speech, and (d) reconstitution (behavioral analysis and synthesis). Extended to ADHD, the model predicts that ADHD should be associated with secondary impairments in these 4 executive abilities and the motor control they afford. The author reviews evidence for each of these domains of functioning and finds it to be strongest for deficits in behavioral inhibition, working memory, regulation of motivation, and motor control in those with ADHD. Although the model is promising as a potential theory of self-control and ADHD, far more research is required to evaluate its merits and the many predictions it makes about ADHD.

/pdf/behavioral-inhibition-sustained-attention-and-executive-3s4ta68l66.pdf

Behavioral inhibition, sustained attention, and executive functions: Constructing a unifying theory of ADHD.

Conduction aphasia and the arcuate fasciculus: A reexamination of the Wernicke-Geschwind model.

Eight patients with acquired agraphia were studied using the same writing tests and were compared with normal and brain-damaged controls. Four patients fulfilled the criteria for lexical agraphia and on CT scan had lesions of the posterior angular gyrus that spared the supramarginal gyrus. The other 4 fulfilled the criteria for phonological agraphia. They had lesions on CT scan that were similar to those found in previously described patients with phonological agraphia. Their lesions involved the supramarginal gyrus or insula deep to it and spared the angular gyrus. These studies support the hypothesis that there are two dissociable spelling systems and that these spelling systems are disrupted by focal lesions in separate but distinct brain regions. Further studies investigated the relationships between phonological agraphia and phonological dyslexia (alexia), and lexical agraphia and surface dyslexia (lexical alexia). The data support the hypothesis that individual systems subserve the four processes of phonological spelling, phonological reading, lexical spelling and lexical reading.

Lexical agraphia. Further support for the two-system hypothesis of linguistic agraphia.

Planum temporale asymmetry and language dominance

Objective: To explore the relationship between morphologic cerebral asymmetries of the pars triangularis (PTr) and the planum temporale (PT) measured on threedimensional, gradient-echo, magnetic resonance imaging scans of healthy right- and left-handed subjects. Design: (Blinded) comparison of healthy right- and left-handed subjects who underwent magnetic resonance imaging. Setting: The Seimens 1-T Magnetom (Seimens, Iselin, NH) at the University of Florida Health Science Center, Gainesville. Subjects: Healthy right-handed (n=8) and left-handed (n=8) subjects matched for age, sex, and educational level. Main Outcome Measures: (1) Average length of the PTr (anterior ascending and anterior descending rami), (2) average length of the PT, (3) asymmetry quotients {[left-right]/[(left+right) (0.5)] } of the PTr and PT, and (4) combined asymmetry quotients of the PTr and PT. Results: There was a significant leftward asymmetry of the PTr and PT in the right-handed subjects, but there was no significant asymmetry in the left-handed subjects. When the combined asymmetry quotient of the PTr and PT was calculated, the right-handed subjects had a leftward asymmetry (87.5% [n=7]) or left was equal to right (12.5% [n=1]), and the left-handed subjects had a leftward asymmetry (62.5% [n=5]), left was equal to right (12.5% [n=1]), or a rightward asymmetry (25% [n=2]). In the left-handed subjects, writing posture seemed to predict these combined asymmetry quotients, ie, left-handed subjects using an inverted writing posture had a leftward asymmetry and left-handed subjects using a noninverted writing posture had a rightward asymmetry of the perisylvian speech-language regions. Conclusions: On three-dimensional, gradient-echo, magnetic resonance imaging scans, we found a significant leftward asymmetry of the PTr and PT. When the groups were divided into right- and left-handed subjects, the former had a significant leftward asymmetry of the PTr and PT, while the latter did not. Measurements of the PTr and PT appear to be important indexes of the known functional asymmetries of the perisylvian speech-language regions.

Morphologic cerebral asymmetries and handedness : the pars triangularis and planum temporale

https://psycnet.apa.org/journals/neu/7/4/433.pdf

Kenneth M. Heilman

Papers

Conduction aphasia and the arcuate fasciculus: A reexamination of the Wernicke-Geschwind model.

Lexical agraphia. Further support for the two-system hypothesis of linguistic agraphia.

Planum temporale asymmetry and language dominance

Morphologic cerebral asymmetries and handedness : the pars triangularis and planum temporale

The nonverbal affect lexicon: Theoretical perspectives from neuropsychological studies of affect perception.