Evidence for involvement of orbitofrontal cortex in memory functions: An interference effect.

Although it is frequently stated that the frontal lobes play a significant role in memory function, research proof has been ambiguous at best. The present study investigated this problem by administering a variety of memory tests (e.g., Wechsler Memory Scale, WAIS) to 16 schizophrenic patients who had undergone prefrontal leukotomy approximately 25 yrs earlier. Ss were divided into 3 groups on the basis of recovery after surgery. Two comparison groups (5 psychiatric and 5 normal controls) were established to control for psychiatric symptomatology, years of institutionalization, age, and years of education. Results indicate that large bilateral orbitofrontal lesions may not result in amnesia; in fact, the nonoperated schizophrenic control group performed the most poorly. Proactive interference was demonstrated, however, resulting in significant impairment for all Ss with prefrontal lobe damage despite normal scores on commonly used memory tests. Ability to maintain consistent and directed attention and to overcome interference is proposed as a role of the frontal lobes in memory function. (55 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Assessment of strategic self-regulation in traumatic brain injury: Its relationship to injury severity and psychosocial outcome.

Standard neuropsychological tests administered in a constrained and artificial laboratory environment are often insensitive to the real-life deficits faced by patients with traumatic brain injury (TBI). The Revised Strategy Application Test (R-SAT) creates an unstructured environment in the laboratory in which environmental cues and internal habits oppose the most efficient strategy, thus mimicking the real-life situations that are problematic for patients with TBI. In this study, R-SAT performance was related both to severity of TBI (i.e., depth of coma) sustained 2–3 years earlier and to quality of life outcome as assessed by the Sickness Impact Profile. This relationship held after accounting for variance attributable to TBI-related slowing and inattention. These findings support the validity of the R-SAT and suggest that behavioral correlates of quality of life outcome in TBI can be assessed in the laboratory with unstructured tasks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Characterization of stability of performance in patients with traumatic brain injury: Variability and consistency on reaction time tests.

The stability of performance of reaction times (RTs) on 3 visual discrimination tasks was assessed in patients with varying severity of traumatic brain injury (TBI) and in matched control Ss. Results were analyzed for group and individual variability and consistency of performance over time. There was significantly greater intersubject (group) variability in the TBI group. Individual patients (intrasubject) tended to be more variable in performance and less consistent over time than control Ss, but this occurred only with specific measures, which suggests that increased lack of stability in performance is not a general impairment after brain damage but requires specific analyses for identification of performance differences. This intrasubject variability was indepedent of test–retest and split-half test reliability. No obvious factors such as severity of brain injury were related to the variability and inconsistency of performance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Organizational strategies with unilateral or bilateral frontal lobe injury in word learning tasks.

To define the capacity to organize verbal learning after frontal lobe injury, 32 patients with stable frontal lesions were evaluated with list learning tasks. Lesion size and site were determined from CAT or magnetic resonance imaging (MRI) scans. The lists were contructed to assess several potential organizational processes. A mild deficit in recognition performance was observed in patients with left frontal lesions accompanied by residual minor language impairments or in patients with septal lesions. Patients with frontal lesions also had a verbal recall deficit that was related to several factors: poor higher order organization of learning, independent of lesion size or site; a selective secondary memory impairment, associated with a language deficit and size of the lesion in the left frontal region; and excess intralist repetitions in patients with right frontal lesions. Impaired list learning after frontal lesions involves several independent psychological processes. This functional heterogeneity is based on regional anatomical specialization and dissociation of task processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Classification of neurological status using multiple discriminant function analysis of neuropsychological test scores.

Neuropsychological measures significantly discriminated 3 a priori defined groups: a control group, a brain-damaged group with a positive neurological exam, and a group with validated brain pathology and a negative physical neurological exam. The neuropsychological indices also correctly discriminated as brain damaged 73.5% of those with negative findings on the neurological exam. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of aging on conditional associative learning: Process analyses and comparison with focal frontal lesions.

Conditional associative learning (CAL), a measure validated in studies of frontal lesions, was used to evaluate the hypothesis that age-related cognitive decline is related to frontal dysfunction. Older adults and focal frontal participants showed impaired CAL performance, but the deficit was greater in the latter group, where it was specific to participants with dorsolateral prefrontal cortical (DLPFC) lesions. The deficits were attributable to strategic rather than basic associative processes. Error scores described ways in which past information failed to guide behavior, and they were related to lesion location. Congruence between older adults and DLPFC participants on a measure of defective inhibition suggests that age-related decline in inhibitory processes is due to DLPFC dysfunction. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neuropsychological studies of the frontal lobes.

Summarizes the current state of knowledge of prefrontal lobe functions as derived from studies and observations of adult humans following frontal lobe damage. Following an overview of the neuroanatomy and neuropathology, frontal lobe activities are presented under the following headings: motor functions; sensory, perception, and construction functions; attention; abnormal awareness; flexibility–perseveration; language; memory; cognition; personality; localization; and hemispheric activity. Six specific prefrontal functions are suggested as the principal disorders underlying many if not all of the described manifestations. Thus, prefrontal damage can (1) separate action from knowledge, (2) impair the ability to handle sequential behaviors, (3) impair the ability to establish or change a set, (4) impair the ability to maintain a set, (5) impair the ability to monitor personal behavior, and (6) produce attitudes of apathy. (5? p ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The course of post-traumatic amnesia: three little words

In November 1996, word reached the University of Washington that Philip Fialkow and his wife, Helen, had died while trekking in Nepal. Over a 30-year period, Dr Fialkow and his colleagues used the cellular mosaicism resulting from X-chromosome inactivation in females as a marker system to investigate the clonal development of human hematopoietic disorders. This review discusses the impact that these studies have had on our understanding of hematopoietic stem cell relationships and the pathogenesis of human neoplasia in general. To appreciate the special role played by studies on clonality, it is necessary to consider how little was known about the origin of leukemias and myeloproliferative disorders and the limited techniques available for their study in the early to mid 1960s. Dr Fialkow and his coworkers were the first to show that myeloproliferative disorders and acute myelogenous leukemias (AML) are clonal diseases at the time of diagnosis and to elucidate the level of differentiation manifested by the originating cell type. Although the myelodysplastic disorders were found to involve a pluripotent stem cell, heterogeneity was found in the level of stem cell involvement in AML. Evidence was obtained to support a multistep pathogenesis of these diseases as well as a clonal but cytogenetically normal stage in some cases of Ph-positive chronic myelogenous leukemia, AML, acute lymphoblastic leukemia and myelodysplasia.     

Chronic obstructive pulmonary disease: effects of hypoxia on neurological and neuropsychological measures

Eighteen patients with chronic obstructive pulmonary disease (COPD) were administered a series of pulmonary, neurological, and neuropsychological measures to test if there was an effect of COPD on neurological and cognitive functioning. Overall, there was no evidence of general dementia in this sample. Measures of immediate and delayed memory, complex attention, and speed of information processing correlated highly with arterial carbon dioxide partial pressure and, to a lesser extent, with oxygen partial pressure. Measures of language abilities, perceptual-motor functioning, and simple attention generally were not related to arterial gas pressures. A similar pattern of findings was obtained when group differences were examined between participants classified as severely hypoxic or mildly hypoxic, although group differences were mitigated by premorbid IQ differences. Hypoxia in COPD results in a relatively focused pattern of impairment in measures of memory function and tasks requiring attention allocation. The memory dysfunction may be related to involvement of limbic memory regions necessary for explicit memory. The attentional deficits were attributed to diffuse brain involvement resulting in reduced resource allocation. Early diagnosis and treatment of the hypoxia is essential.     

Toward a theory of episodic memory: The frontal lobes and autonoetic consciousness.

Adult humans are capable of remembering prior events by mentally traveling back in time to reexperience those events. In this review, the authors discuss this and other related capabilities. considering evidence from such diverse sources as brain imaging, neuropsychological experiments, clinical observations, and developmental psychology. The evidence supports a preliminary theory of episodic remembering, which holds that the prefrontal cortex plays a critical, supervisory role in empowering healthy adults with autonoetic consciousness—the capacity to mentally represent and become aware of subjective experiences in the past, present, and future. When a rememberer mentally travels back in subjective time to reexperience his or her personal past, the result is an act of retrieval from episodic memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)