The effects of clozapine on delayed spatial alternation deficits in rats with hippocampal damage

Clozapine is an atypical antipsychotic drug that has been shown to improve spatial memory in some animal models; however its efficacy in reversing spatial memory impairment in rats with hippocampal lesions is unknown. To address this issue, we tested the effects of clozapine on delayed spatial alternation deficits in rats with hippocampal damage in three separate experiments. In each experiment, adult male rats received sham surgery or direct stereotaxic infusions of the excitotoxin, NMDA, into the hippocampus. In the first study, seven days after surgery, the sham control animals received daily saline injections while the lesioned animals were split into two groups that received daily saline or clozapine (2.0 mg/kg, sc) injections. During the fifth week of injections, all animals were tested in a food-motivated delayed spatial alternation task. Saline-treated rats with excitotoxic hippocampal damage displayed significant deficits in delayed spatial alternation. Daily clozapine injections completely reversed this deficit. In a second experiment, it was found that clozapine treatment limited to the testing days only did not improve alternation performance in lesioned rats. Finally, in a third experiment, chronic clozapine treatment did not improve alternation performance in lesioned rats that were pre-trained in the alternation task prior to surgery. These results suggest that chronic, but not acute, clozapine treatment enables rats with hippocampal damage to develop new spatial learning, but can not rescue old spatial learning established prior to damage. These results may have implications for the treatment of cognitive deficits caused by hippocampal dysfunction in disorders such as schizophrenia, Alzheimer's disease, and others.     

Ecological Neuropsychology: An Alternative to the Deficit Model for Conceptualizing and Serving Students with Learning Disabilities

The present paper contends that children with learning disabilities are better served when assessment and intervention are conceptualized within an ecological neuropsychology perspective than within the traditional deficit model perspective, which is the predominant approach to intervention in medical and educational settings. The deficit method conceptualizes problems as within the child, and the major consequence of this approach is that little time is spent analyzing the learning environment or other systems that might impact the child's ability to be successful in an academic setting. Therefore, rehabilitation efforts have had limited success. In contrast, ecological neuropsychology is a strength-based approach that considers the child, as well as the systems within which he/she interacts, when assessing, diagnosing, and intervening with students who are experiencing learning difficulties.     

An investigation of the relationship between eye and retinal image movement in the perception of movement

The question investigated was whether or not eye movements accompanied by abnormal retinal image movements, movements that are either or both at a different rate or in a different direction than the eye movement, predictably lead to perceived movement. Os reported whether or not they saw a visual target move when the movement of the target was either dependent on and simultaneous with their eye movements or when the target movement was independent of their eye movements. In the main experiment, observations were made when the ratio between eye and target movement fem/tm) was 2/5, 1/5, 1/10, 1/20, and 0. All these ratios were tested when the direction of the target movement was in the same (H+), opposite (H?), and at right angles to (V+, V?) the movement of the eyes. Eye movements, target movements, and reports of target movement were recorded. Results indicate that a discrepancy between eye and target movement greater than 20% predictably leads to perceived target movement, whereas a discrepancy of 5% or less rarely leads to perceived movement. The results are interpreted as support for the operation of a compensatory mechanism during eye movements.     

Personality disorders and response to outpatient treatment of chronic pain

As part of a comprehensive interdisciplinary evaluation conducted prior to participation in an outpatient chronic pain treatment program, the psychological status of 101 persons was assessed. The majority of participants was found to have a form of personality disorder, determined by conservative cutoff scores applied to their Millon Clinical Multiaxial Inventory (MCMI) profiles. DSM-III-R Cluster C disorders (i.e., Avoidant, Dependent, Obsessive-Compulsive, and Passive-Aggressive) were overrepresented in this sample. Subsequent analyses revealed that personality disorders were related to higher levels of self-reported distress and pain at both the beginning and the end of outpatient treatment. Differential responses to treatment were observed on self-report measures; however, few relations were found between personality disorder and physical therapist ratings of impairment and improvement. Implications for the assessment of personality disorders in outpatient pain treatment programs are discussed and appropriate intervention strategies are considered.     

A comparison of lexical-semantic impairments in left hemisphere stroke and Alzheimer's disease

Patients with aphasia due to left hemisphere stroke and patients with Alzheimer's disease, who were matched for severity of naming impairment, were compared on tests of lexical-semantic processing. The results suggest that the lexical-semantic impairments in both groups are due to a combination of impaired access to, and loss of, lexical-semantic information, but that impaired access is more prominent in stroke patients, whereas Alzheimer's disease patients suffer a greater loss of information. The results are discussed in terms of a brain model of the storage and processing of lexical-semantic information, and with respect to implications for treatment strategies.     

A re-examination of the Stratton effect: Egocentric adaptation to a rotated visual image

The question raised by Stratton, whether a disoriented image can yield upright vision. was explored by exposing Os to a prismatically rotated field. To isolate the problem ofadaptation to altered egocentric orientation, the O’s view was restricted to a horizontal plane during both prism exposure and test. Significant adaptation based on movement-derived information was obtained.     

The role of movement in perceptual adaptation to a tilted retinal image

Attention, Perception, & Psychophysics - Perceptual adaptation to prismatically created tilt of the retinal image was measured after three conditions of exposure: active, passive and no...