Semantic memory deterioration is a major component of the cognitive decline seen in patients with dementia of the Alzheimer's type (DAT); however, the exact nature of this deficit remains unclear. Some research data support a procedural deficit where there is an inability to access or retrieve the contents of semantic memory, while other data point to a degraded semantic store where the actual content of semantic memory is degraded. Additional information about semantic processing in DAT can be obtained through the use of an event-related potential (ERP) component known as N400. In the present study, ERPs were recorded from 10 young control participants, 10 elderly control participants, and 10 DAT patients in a picture–semantic matching task. Stimuli were presented sequentially as prime–target pairs, with one-half of the targets matching the primes via semantic relationships (e.g., piano–violin) and the other half mismatching the prime (e.g., helmet–violin). The task was to discriminate between semantically related and unrelated pairs of pictures. In the young and elderly control groups, ERPs generated a larger N400 for unrelated than related target pictures, with a maximum amplitude around 380 ms in the young group and around 480 ms in the elderly group. The amplitude of the N400 was significantly reduced in the DAT patients. However, a separate analysis of congruent and incongruent ERPs trials revealed significant differences only with the incongruent trials. The amplitude of incongruent recordings was larger for the elderly control group than for the DAT patients, while the amplitude for congruent recordings was similar in both groups. These findings are consistent with the neuropathological evidence that Alzheimer's disease is a neocortical disconnection syndrome in which there is a loss of structural and functional integrity of long corticocortical tracts. The semantic activation created by the context is not used efficiently in processing stimuli, which affects access to specific concepts and gradually leads to a breakdown in the structure and organization of semantic memory. (JINS, 1998, 4, 415–425.)

While response slowing on psychological tasks is a symptom of both depression and Alzheimer's disease (AD), the underlying mechanisms may be quite different: a slowing of cognitive processing in AD and a motor retardation in depression. This hypothesis was tested by examining the rate at which participants performed a simple cognitive operation: subvocal pronunciation. Participants were shown words of between one and three syllables and were asked to decide whether each word ended in a particular sound. This task required participants to transform the written word into its phonological representation, an operation thought to involve subvocal pronunciation. Decision time rose linearly with the number of syllables in all three subject groups. The linear function of the AD patients had a significantly greater slope, indicating a slower rate of subvocal pronunciation, whereas the slope was the same for the normal old and depressed. Both the depressed and AD patients had a higher intercept than the normal old, suggesting a sensorimotor slowing. After treatment, the intercept of the linear function for depressed patients fell, but there was no change in the slope. Thus, this study suggests that AD produces a slowing in both cognitive and motor processes, whereas depression results solely in a motor retardation. (JINS, 1998, 4, 426–434.)

Priming for line drawings of real and nonreal objects was examined in an object decision task for 16 patients with Alzheimer's disease (AD) and 16 normal elderly control (NC) participants. In two study phases, participants decided if objects were real or nonreal. In an implicit test phase, real/nonreal decisions were made for studied and unstudied objects, and priming was measured as the difference in decision speed or accuracy between studied and unstudied objects. In an explicit test phase, yes/no recognition was measured for real and nonreal objects. AD patients had impaired explicit memory for real and nonreal objects and intact repetition priming for real objects. By the latency measure, both AD and NC groups showed priming for nonreal objects but in opposite ways. Classification decisions about studied relative to nonstudied nonreal objects were slower for the AD patients, whereas such decisions were faster for the NC participants. Classification decisions of both groups were less accurate for repeated nonreal objects. These results support the claim that AD patients with mild cognitive impairment show normal perceptual priming. The AD inhibition for studied nonreal objects is discussed in terms of the decision conflict that occurs when recollection of source is not available to counter the influence of familiarity. (JINS, 1998, 4, 435–446.)

Neuropsychological research indicates that the left hemisphere plays a dominant role in verbal production and processing, while the right hemisphere plays a dominant role in nonverbal production and processing. This study sought to examine the effects of such differential hemispheric specialization on personality and social competency. Ten left hemisphere damaged (LHD) stroke patients, 11 right hemisphere damaged (RHD) stroke patients, and 7 neurologically normal (NHD) patients were videotaped while engaging in social interaction with their spouse and an interviewer. Segments of the interactions were independently coded by two observers. Patients and spouses were rated with respect to their level of social competency and the extent to which they were characterized by 10 personality adjectives (e.g., outgoing, warm). Ratings for the personality items were summed to create an aggregate score. Analysis of these scores revealed both LHD and RHD patients to have lower (i.e., more negative) mean scores than NHD patients, suggesting that stroke patients as a whole were seen as socially impaired. Analysis of the socially competent item revealed particular LHD deficits; LHD patients were seen as less socially competent than both RHD and NHD patients. Spouses of LHD, RHD, and NHD patients, in contrast, did not differ in observer-rated social behavior. (JINS, 1998, 4, 447–455.)

Former neuropsychological studies with Chronic Fatigue Syndrome (CFS) patients evaluated a broad range of cognitive functions. Several, but not all, reported subtle attentional and memory impairments suggesting possible mild cerebral involvement. In this study, a battery of attentional tests and a verbal memory task were administered to 20 CFS patients and 22 healthy controls (HC) in order to clarify the specific nature of attention and memory impairment in these patients. The results provide evidence for attentional dysfunction in patients with CFS as compared to HC. CFS patients performed more poorly on a span test measuring attentional capacity and working memory. Speeded attentional tasks with a more complex element of memory scanning and divided attention seem to be a sensitive measure of reduced attentional capacity in these patients. Focused attention, defined as the ability to attend to a single stimulus while ignoring irrelevant stimuli, appears not to be impaired. CFS patients were poorer on recall of verbal information across learning trials, and poor performance on delayed recall may be due to poor initial learning and not only to a retrieval failure. (JINS, 1998, 4, 456–466.)

Recent studies have detected basal ganglia atrophy in clinically asymptomatic persons with the genetic mutation that causes Huntington's disease (HD). Whether reductions in caudate and putamen volume on MRI scans are associated with changes in cognitive and neurologic functioning was examined in 13 healthy adults with the IT-15 mutation. Reduced striatal volume was found to correlate with greater neurologic (largely motor) impairment, slower mental processing speed, and poorer verbal learning, although none of the participants met even liberal criteria for clinical diagnosis of HD. These correlations are strikingly similar to those observed in symptomatic HD patients, possibly reflecting the earliest manifestations of disease. (JINS, 1998, 4, 467–473.)

Several tests from the CANTAB neuropsychological test battery previously shown to be sensitive to frontal lobe dysfunction were administered to a large group of normal volunteers (N = 341) ranging in age from 21 to 79 years. The main tests included a computerized form of the Tower of London test of planning, a self-ordered spatial working memory task, and a test of attentional set formation and shifting. A computerized form of the Corsi spatial span task was also given. Age-related graded declines in performance were seen, sometimes in a discontinuous manner, especially for the attentional set shifting task (at the extradimensional shift stage). Patterns of deficits reminiscent of frontal lobe or basal ganglia damage were observed in the oldest age group (74–79). However, overall the data were only partially consistent with the hypothesis that frontal lobe functions are the most sensitive to effects of aging. Factor analyses showed that performance in the executive tests was not simply related to a measure of fluid intelligence, and their performance had a factor loading structure distinct from that for the CANTAB tests of visual memory and learning previously administered to the same sample. Finally, only limited support was found for the hypothesis that cognitive aging depends on slowed information processing. (JINS, 1998, 4, 474–490.)

The cerebellum's role in cognitive skills was examined in a child (L.C.) with focal injury to the left cerebellum. Initial symptoms included aphasia and dysarthria. At 3 and 9 months post-injury, clinical neuropsychological tests revealed persistent psychomotor slowing as well as deficits in executive functions. Further cognitive testing at 13 and 16 months post-injury demonstrated that L.C. processed information from both the linguistic and nonlinguistic domains more slowly than age-, grade- and sex-matched controls. Notably, her linguistic processing was more than twice as slow as that of her peers, whereas her nonlinguistic processing was only approximately 20% slower. Within each domain the degree of cognitive slowing was approximately the same across diverse tasks. These results are consistent with the hypothesis of a cerebellar contribution to cognitive processing, particularly the processing of linguistic information. (JINS, 1998, 4, 491–501.)

Recognition memory for words and designs was assessed in epilepsy patients who underwent unilateral anterior temporal lobectomy. Memory was assessed during the intracarotid amobarbital test (IAT) performed prior to surgery and also following surgery. Memory discrimination and response bias lateralized differently. Memory discrimination, or memory accuracy, lateralized as a function of the type of material used in memory testing. Left temporal lobe lesions resulted in more impaired discrimination of verbal materials; right temporal lobe lesions resulted in more impaired discrimination of visuospatial materials. Response bias, the decision rule adopted in situations of uncertainty, was more liberal following left temporal lobe lesions for both verbal and visuospatial materials. Findings suggest that the two cerebral hemispheres are differentially specialized for encoding different types of information in long term memory, and that this impacts on decision strategies in situations of memory uncertainty. (JINS, 1998, 4, 502–511.)

This study describes changes in cognitive function in patients who are typically excluded from longitudinal studies due to their inability to complete most standardized batteries. Thirty-three patients with moderate to severe Alzheimer's disease were assessed by means of the Severe Impairment Battery (SIB), Mini Mental State Examination (MMSE), Clinical Dementia Rating (CDR), and measures of functional status. Follow-up evaluations were conducted, and annual rates of change were calculated. Patients with severe cognitive impairment demonstrated rates of progression similar to patients who were moderately impaired at initial evaluation. Rates of decline on the SIB were unrelated to baseline cognitive function, and annual rate of decline in Year 1 was not correlated with disease progression in the subsequent year. This study demonstrates that, with appropriate assessments, severely impaired patients can exhibit a range of performance and rates of decline that are comparable to those of moderately impaired patients. (JINS, 1998, 4, 512–516.)

Fortunately, it is the rare neuropsychologist who still uses the term “frontal lobe functions” to refer to the collection of supervisory and regulatory mental processes we now typically call the “executive functions.” Most of us have come to realize that simply using a neuroanatomic moniker for a set of cognitive processes does not a neuropsychology make.

In this article I critically review the concept of the central executive. I argue that the experimental evidence for a central executive lacks rigor to the point where it is an unfalsifiable construct. I examine the neuropsychological and neuroradiological evidence and demonstrate that there is no localization evidence for a central executive. What emerges instead is a pattern of extensive heterogeneity with different executive tasks associated with different neural substrates. In sum it is argued that the idea of a central executive should be abandoned, and, from a neuropsychological perspective, tests that purport to measure executive function should do so in a qualitative way rather than assume that a range of tests load on a unitary dimension of performance. (JINS, 1998, 4, 518–522.)

Parkin's criticisms of the central executive are based on a series of misconceptions. The central executive is not an organ that might or might not exist, but a scientific concept. Part of its function is to separate the analysis of executive processes from the question of their anatomical location. Like other components of working memory, it is fractionable into subsystems. How the subsystems interrelate and how they map onto the anatomical substrate are empirical questions under active current investigation. (JINS, 1998, 4, 523–526.)

Cerebral plasticity is perhaps the most fundamental principle of neuropsychology that is invoked, measured, analyzed, and targeted for treatment and experimental intervention each day by clinicians and scientists. Whether the focus is central nervous system development, recovery from brain damage, or age-associated changes and diseases, understanding cerebral plasticity is vital to scientific and clinical advances in human brain function and treatment of neurologic disorders in millions of people. Some of these advances have been succinctly summarized in two recent volumes. The first (McGaugh et al.) is a handsomely bound summary of basic research investigating brain mechanisms underlying learning and memory. The text resulted from a symposium featuring largely American and Mexican investigators who addressed cellular aspects of memory and how brain systems may mediate different types of memory. As John Garcia emphasizes in the opening chapter, such investigation is driven by the need to interrelate behavior and brain processes, bridging the barranca or chasm between behavioral and brain research. The fundamental role of learning and memory to behavior of all varieties, and the widespread involvement of cortical, limbic, basal ganglia, diencephalic, brain stem, and cerebellar structures in memory provides the massive playing field on which the ensuing behavioral, electrophysiologic, neurochemical, and molecular studies are described.

Charles G. Matthews will be missed for his enormous contributions to clinical neuropsychology, but even more for his wisdom, integrity, wit, humility, compassion, and eloquence. It was these personal characteristics which made Chuck an extraordinary, yet quiet leader. His influential role in the inception and continuing development of our major organizations earned him a position among our profession's “Founding Fathers.” He was president of Division 40 (1989), INS (1991), and ABCN (1991–1993), but his influence spanned decades. He quietly served behind the scenes as an advisor to presidents of these organizations who recognized his perspicacity and ability to see all sides of a given issue.