Parallel distributed processing and neuropsychology: A neural network model of Wisconsin card sorting and verbal fluency

Neural networks can be used as a tool in the explanation of neuropsychological data. Using the Hebbian Learning Rule and other such principles as competition and modifiable interlevel feedback, researchers have successfully modeled a widely used neuropsychological test, the Wisconsin Card Sorting Test. One of these models is reviewed here and extended to a qualitative analysis of how verbal fluency might be modeled, which demonstrates the importance of accounting for the attentional components of both tests. Difficulties remain in programming sequential cognitive processes within a parallel distributed processing (PDP) framework and integrating exceedingly complex neuropsychological tests such as Proverbs. PDP neural network methodology offers neuropsychologists co-validation procedures within narrowly defined areas of reliability and validity.     

Is anorexia nervosa a neuropsychological disease?

Evidence for central nervous system, and more particularly cortical, etiology of anorexia nervosa is reviewed. Topics covered are neuropsychiatric comorbidity, inheritance patterns, the neurobiology of body-image disturbance and of the eating function, perinatal and alcoholic insult to the brain, neurochemical and neuroelectric disturbance, anatomic and metabolic brain imaging, and neuropsychological impairment. It is concluded that there is indeed an important neuropsychological etiological dimension to anorexia nervosa. The profile most frequently associated with anorexia nervosa is right posterior hypometabolism, followed by right anterior hypermetabolism, both associated with right-sided abnormal electroencephalogram spiking. It is also proposed that bulimia consists of a positive neurological subtype and that restricting anorexia represents a negative neurological subtype. Priorities for further research into anorexia nervosa are specified to include twin adoption studies, brain electrical topography studies, postmortem histological studies, and experimentally inspired neuropsychological studies.     

A brief neuropsychological screening battery to detect brain damage in a psychiatric population

Seventy-five patients admitted to the psychiatric unit of a general hospital were administered a brief neuropsychological screening battery. Discharge diagnoses obtained from the medical records revealed that 20% had brainbased pathology. A discriminant function analysis resulted in a five-variable model (Symbol-Digit Modalities Test, educational level, Psychiatric-Organic subscale of the MMPI, and Shipley Vocabulary and Abstraction scores) which correctly classified 84% of the subjects, with 87% correct identification of the brain-damaged group. A jackknife cross-validation procedure resulted in comparable hit rates.     

Information processing,neuropsychological function,and the inherited predisposition to alcoholism

Sons of male alcoholics are at particularly heightened risk for the development of alcoholism. This heightened risk frequently appears in association with increased incidence of conduct disorder or hyperactivity, with deficits in abstract thinking and poor school performance, with abnormalities in cued psychophysiological response, and with increased sensitivity to the putatively stress-response-dampening effects of alcohol intoxication. This risk and its associated features are discussed within the context of a neuropsychological theory, predicated on the notions (1) that deficits in cognitive functions theoretically dependent upon the intact functioning of the prefrontal cortex could underlie manifestation of the idiosyncracies commonly attributed to sons of male alcoholics, and (2) that acute alcohol intoxication could relieve the subjective discomfort associated with the consequences of such deficits.     

Neuropsychiatric and experiential correlates of violent juvenile delinquency

This article reviews evidence regarding contributions of neuropsychiatric and psychological vulnerabilities to violent delinquency, and the interaction between intrinsic vulnerabilities and experiential factors in the genesis of antisocial juvenile behavior. Consideration is given to biochemical and physiological factors, genetics, medical status, and neurological, psychiatric, and neuropsychological factors. Implications for treatment are discussed.     

Neuropsychological identification of motor problems: Can we learn something from the feet and legs that hands and arms will not tell us?

The degree of structural and functional specialization that differentiates between upper and lower limb use in humans is quite unparalleled among primates. It is argued that less neural resources are devoted to leg and foot control than to arm and hand control, and that this aspect of lower limb innervation, together with the uniquely restricted use of the lower limb, renders lower limb function more sensitive to general neural insult. In addition, the status of leg and foot control differs from that of arm and hand control both early in life and during the later years of decline.     

The Future of Neuropsychology in Medical Specialties

Although neuropsychology continues to grow as a valued service in most medical specialties, because of its multiple uses with diverse populations, it is necessary to evaluate the specialty critically in order to ensure continued future success. This article reviews areas in which neuropsychology is most firmly established, potential growth areas, and likely obstacles to success in the future. Suggestions are provided for ways in which neuropsychology can be improved/adapted in clinical, business, research, and training areas. On sabattical at Bebek University, Instanbul, Turkey     

Cognitive sequelae of repeated head injury in a population of intravenous drug users

The relationship between closed head injury and performance on neuropsychological (NP) tests was investigated in a group of intravenous drug users (IVDUs). Subjects with repeated head traumas involving loss of consciousness (LOC) performed worse than both a control group without LOC and reference group with only a single episode of LOC. There were no significant differences between the last two groups. Performance on tests of memory, attention, and motor performance was significantly worse in the group with repeated head injury. The average time since the last episode of LOC was more than 11 years. We conclude from these findings that a single episode of LOC does not result in significant cognitive impairment in this population. Two or more episodes, however, are more likely to produce chronic cognitive impairment.     

Neurobehavioral deficits,adolescent traumatic brain injury,and transition to college

Outcome following traumatic brain injury (TBI) has been frequently evaluated for adults, although there has been minimal research on adolescents with TBI. It has been argued that TBI sequelae may be more difficult for adolescents to adjust to given developmental changes in physical (puberty), interpersonal (self-concept), and environmental domains (transition to college). In addition, it is commonly acknowledged that moderator variables such as psychiatric history, family functioning, substance use, and sexuality impact functional outcome following TBI, although it is often difficult to objectively evaluate these variables. The current study examined relationships among TBI-related deficits, moderator variables, and academic outcomes for six adolescents transitioning to college. The findings suggest that it may not be appropriate to predict functional outcome based solely on objective neuropsychological results. However, moderator variables appear to have a more direct relationship with outcome, depending on the moderator variable and the individual.     

Toward the neural basis of verbal priming: A cognitive-neuropsychological synthesis

Repetition priming is a mnemonic phenomenon that has attracted considerable attention from neuropsychologists and cognitive scientists. In an attempt at elucidating the putative mechanisms of priming, the present review draws on evidence from both domains. The review is restricted to verbal priming of visually presented stimuli—an area that accounts for the majority of empirical studies of priming. A number of theoretical accounts are presented. The interim conclusion is that neither multiple systems nor unitary system-multiple process theories can adequately explain the data on priming, although both contain many valid components. An integrative model is proposed to improve the explanation of the empirical evidence. The central assertion of the proposed model is that repetition priming depends on perceptual processes that can be mapped on specific neural systems. It is postulated that individual differences in perceptual processing ability predict variability in memory performance. It is proposed that data-driven priming of verbal stimuli critically depends on the activity of primary and secondary visual cortices in the right hemisphere, whereas conceptually-driven priming is hypothesized to rely on the activities of higher order tertiary association cortices in language areas and more anterior neocortical areas.