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.

/pdf/the-attention-system-of-the-human-brain-w797wllpat.pdf

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.

To the Editor: In their review of acute cerebellar hemorrhages (NEUROLOGY 27527 .532 , 1977), Drs. Brennan and Bergland commented on the uniformly poor prognosis of comatose patients whose intrinsic brainstem reflexes fail at the time of surgery. Although this is undoubtedly true in the vast ma.jority of cases. I would like to mention two cases of children with spontaneous cerebellar hemorrhages who survived even though they were in extremis on admission to the hospital.’ The children. who were 8 and 9 years old, were comatose, had irregular respiratory patterns, and had no oculovestibular responses to cold water. A hematoma was surgically evacuated from each patient, and both children survived with moderate deficits. Hypertension is the cause of the cerebellar hemorrhage in most adults. In contrast, small angiomatous malformations are responsible for most cases of nontraumatic cerebel lar hematomas in children. Such a malformation was found in one of the above cases. The reason that both children were able to survive in spite of coma and the absence of intrinsic brainstem reflexes is unknown. but it may be related to the fact that they did not have chronic underlying disease such as hypertension. The point to be emphasized, however, is that surgical intervention should be attempted in all cases, even when the prognostic indicators all point to a poor outcome.

Factors in affective discrimination of speech

have been reported in association with psychiatric diseases, brain stem strokes, deafness, degenerative diseases, intoxications, pharmacologic agents, and epilepsy. We present a patient who in the ...

Musical hallucinations with a right frontotemporal stroke

Background/Objective: Attended objects are perceived as having a greater magnitude than those which receive less attention. Rightward deviation on line bisection (allocentric neglect), is results from right hemisphere lesions. In contrast, healthy participants reveal a leftward deviation in visual and tactile line bisection (pseudoneglect), both allocentric tasks. These results suggest that the right hemisphere is dominant in allocating spatial attention. With an egocentric task, such as body bisections, there is a rightward deviation, suggesting left hemisphere dominance for mediating egocentric attention; however, it is possible that this rightward deviation is action-intentional rather than attentional. Thus, it is not known if in a non-motoric, non-spatial, purely perceptual domain there is an attentional bias and the direction of this bias.
Design/Methods: The participants were 24 healthy adults (14F). To test these hypotheses we used a psychophysical technique where one compares the intensity of test stimuli to a standard stimulus. These test stimuli were applied to the palm of the left and right hands, in a counterbalanced order, using Semmes-Weinstein Monofilaments of 6 magnitudes, 3 greater and 3 less than a standard stimulus. In each trial, after being stimulated with the standard stimulus, a test monofilament was applied and the participant was asked to provide a numerical estimate of the magnitude of the second stimulus relative to the standard.
Results and Conclusions: The right hand perceived stimuli that were lighter than the standard stimulus to be more intense than when these same stimuli were perceived by the left hand. Both this tactile task and the body bisection task, where there is a rightward deviation, require attention to be egocentrically oriented. These results suggest that whereas the right hemisphere is dominant for mediating allocentric or spatial attention the left hemisphere may be domain for mediating egocentric or self-directed attention Disclosure: Dr. Kesayan has nothing to disclose. Dr. Lamb has nothing to disclose. Dr. Williamson has nothing to disclose. Dr. Falchook has nothing to disclose. Dr. Heilman has received personal compensation from AAN, Harvard Dementia as a speaker. Dr. Heilman has received royalities on books that he has written or edited.

Perceptual Pseudoneglect: Laterality and the Perception of Tactile Pressure (P4.056)

BACKGROUND Emotions and moods are often expressed using verbal, vertical spatial metaphors (eg, "I'm feeling down"). The reason for using these vertical metaphors is unknown; however, when individuals experience depressive symptoms, they often become self-reflective and ruminative. These mental activities are associated with activation of the default network, including the parietal lobes. The parietal lobes are a critical component of the dorsal visual attentional network, which allocates attention downward. Therefore, activation of the default network may create a downward bias of vertical attention. OBJECTIVE To investigate whether depressive mood disposition, as measured by the number of depressive symptoms experienced by an individual, influences their allocation of vertical attention. METHODS We used the Hospital Anxiety and Depression Scale to evaluate depressive symptoms in 48 right-handed individuals with a mean age of 57.31 (±17.14) years. We also asked the participants to mark the center (bisect) of 24 vertical and 24 horizontal lines. RESULTS Overall, the individuals deviated their bisections of vertical lines upward (M=2.66 mm; SD=3.85). A stepwise linear regression analysis revealed that the number of depressive symptoms an individual experienced was significantly associated with a reduction in the magnitude of this upward vertical bias (P=0.009; R=0.138), such that the number of depressive symptoms was associated with the reduction (lowering) of their upward bias. CONCLUSION Depressive symptoms may be associated with a relative lowering of the vertical attentional bias, and this lowering may be related to increased activation of portions of the default network.

Feeling and Looking Down: Impact of Depressive Symptoms on the Allocation of Vertical Attention.

Fredrich August von Kekule, a famous German chemist, was attempting to determine the shape of the benzene molecule, which was known to have six carbon atoms. In 1865, reflecting upon his discovery of the hexagonal-ring like structure, he asserted that the solution came to him in a dream1; however, it is not clear if he was in rapid eye movement (REM) sleep dreaming or if he was in non-REM (NREM) sleep imagery. It is possible to think of this type of discoveries as an expression of creativity, i.e. the ability to use existing pieces of information and combine them in novel patterns leading to greater understanding and new solutions. Preliminary support of the role of sleep in creative thinking comes from a recent study by Wagner et al.2; these authors asked normal participants to perform a cognitive task, the Number Reduction Task. In this task, participants are required to understand a set of stimulus-response sequences and supply a single representative numerical answer. Improvement in task performance may be gradual (i.e., by slowly increasing response speed), or abrupt (after insight into an abstract rule underlying all sequences). They found that 59% of the participants that were allowed to sleep were able to perform the task in a time that was 70% shorter than the other group that did not sleep and suggested that sleep may facilitate insight-related problem solving. Here we report the results of the first study showing a direct complex correlation between sleep architecture or microstructure and creativity in normal controls.

Kenneth M. Heilman

Papers

Factors in affective discrimination of speech

Musical hallucinations with a right frontotemporal stroke

Perceptual Pseudoneglect: Laterality and the Perception of Tactile Pressure (P4.056)

Feeling and Looking Down: Impact of Depressive Symptoms on the Allocation of Vertical Attention.

The Correlation between Sleep and Creativity