Lisa A. Morrow

Parietal lobe mechanisms of spatial attention: Modality-specific or supramodal?

Is the spatial attention system divided into separate, modality-specific subsystems, or is there a supramodal spatial attention system? More specifically, does the role of the parietal lobe in spatial attention involve modality-specific or supramodal mechanisms? We addressed this question using a variant of Posners spatial cuing task. Parietal-lesioned patients performed a simple reaction time task to lateralized visual target stimuli, preceded on each trial by either non-predictive lateralized visual cue stimuli or non-predictive lateralized auditory cue stimuli. With both types of cues, we found disproportionate slowness in responding to invalidly cued contralesional targets, indicative of an impairment in disengaging attention from the ipsilesional to the contralesional side of space. The finding of an attentional disengagement impairment for visual targets with auditory cues implies that the parietal lobes attentional mechanism operates on a representation of space in which both visual and auditory stimuli are represented, in other words, a supramodal representation of space.

Building-associated pulmonary disease from exposure to Stachybotrys chartarum and Aspergillus versicolor.

The authors present an outbreak of disease associated with exposure to Stachybotrys chartarum and Aspergillus species. A courthouse and two associated office buildings had generated discomfort among employees for two years since initial occupancy. Multiple interventions had been unsuccessful An initial evaluation of 14 individuals identified three with potential asthma and three with symptoms consistent with interstitial lung disease. A clinical screening protocol to identify individuals who should be removed from work identified three likely and seven possible cases of building-related asthma. Detailed environmental and engineering assessments of the building identified major problems in mechanical system design, building construction, and operational strategies leading to excess moisture and elevated relative humidities. Moisture-damaged interior surfaces in both buildings were contaminated with S. chartarum, A. versicolor, and Penicillium species. Aspergillus species, especially A. versicolor, at concentrations of 10(1) to 10(4)/m3 dominated the indoor air under normal operating conditions. Bulk samples also revealed large quantities of Stachybotrys. A questionnaire survey of the three case and two control buildings documented between three- and 15-fold increases in symptoms. A nested case-control study suggested emphysematous-like disease in individuals meeting questionnaire definitions for cases. Replication of analysis strategies used in similar previous investigations suggested an association between worsening symptoms and decreased diffusing capacity of the lung. Performance on neuropsychological measures was similar for both cases and controls, although workers with symptoms reported increased levels of current but not past psychiatric symptomatology. Chemical analyses demonstrated the presence of satratoxins G and H. Cytotoxic laboratory analyses demonstrated the presence of agents with biological effectiveness in bulk materials. No association was seen between IgE or IgG antibodies and the presence of disease. This outbreak represents a likely human response to inhaled fungal toxins in indoor environments. Moisture indoors represents a public health issue currently inadequately addressed by building, health, or housing codes.

The disengagement of covert attention and the neglect syndrome

Parietal lesions can cause impairment of the ability to disengage attention from an ipsilateral stimulus prior to shifting the focus of attention contralaterally. The present study addresses two main questions concerning the parietal-based disengagement process. First, what is the relationship between the disengagement process, as operationalized by a cued simple reaction-time task, and the neglect syndrome? Second, is there an asymmetry in the roles of the left and right hemisphere in the disengagement of attention? We found a very strong relationship between clinical neglect and impairment of the disengagement operation across patients, and longitudinally, within patients. Furthermore, we found that right-hemisphere lesions cause greater impairment in the disengage process than do left-hemisphere lesions.

Alterations in cognitive and psychological functioning after organic solvent exposure

Exposure to organic solvents has been linked repeatedly to alterations in both personality and cognitive functioning. To assess the nature and extent of these changes more thoroughly, 32 workers with a history of exposure to mixtures of organic solvents and 32 age- and education-matched blue-collar workers with no history of exposure were assessed with a comprehensive battery of neuropsychological tests. Although both groups were comparable on measures of general intelligence, significant differences were found in virtually all other cognitive domains tested (Learning and Memory, Visuospatial, Attention and Mental Flexibility, Psychomotor Speed). In addition, Minnesota Multiphasic Personality Inventories of exposed workers indicated clinically significant levels of depression, anxiety, somatic concerns and disturbances in thinking. The reported psychological distress was unrelated to degree of cognitive deficit. Finally, several exposure-related variables were associated with poorer performance on tests of memory and visuospatial ability.

Assessment of Neuropsychological Dysfunction in the Workplace: Normative Data from the Pittsburgh Occupational Exposures Test Battery

Neuropsychologists are being increasingly called upon to assess the neurobehavioral status of adults who have been exposed to toxic chemicals or heavy metals in the workplace. Unfortunately, the evaluation of blue-collar workers has been hampered by the absence of a brief yet comprehensive battery of sensitive neuropsychological tests that have been administered to a large cohort of demographically similar adults with no prior history of occupational exposure. In this paper we describe the development of the Pittsburgh Occupational Exposures Test Battery. We detail the procedures used to collect appropriate age-scaled norms from 182 blue-collar males, and delineate the factor structure of the test battery. We also examine the interrelationships among test scores and certain demographic variables, and discuss the epidemiologic and clinical relevance of these data.

Chronic Pain Is Associated with Brain Volume Loss in Older Adults: Preliminary Evidence

OBJECTIVES The primary aim of this pilot investigation was to identify structural brain differences in older adults with chronic low back pain (CLBP) as compared with pain-free individuals. DESIGN Cross-sectional, case-control. PARTICIPANTS Sixteen cognitively intact older adults, eight with CLBP and eight pain-free; excluded if with psychiatric or neurological disorders, substance abuse, opioid use, diabetes mellitus, and/or hypertension. METHODS Brain magnetic resonance imaging (MRI) and tests of neuropsychological performance (digit span, digit symbol substitution, letter-number sequencing, trail making) were administered to all participants. Gray matter (GM), white matter (WM), cerebrospinal fluid, and corpus callosum (CC) volumes were measured as a percentage of total supratentorial intracranial volume. Voxel-based morphometry analysis of GM and WM assessed regional differences. RESULTS Between-groups analysis revealed a non-significant trend toward decreased middle CC volume in the CLBP group (1.43E-03 +/- 2.67E-04, 1.63E-03 +/- 2.00E-04: P = 0.09). Regional analysis in the CLBP group demonstrated significantly decreased GM volume (P < 0.001) in the posterior parietal cortex and middle cingulate WM volume (P < 0.001) of the left hemisphere. CLBP participants performed significantly worse on digit span forward (P = 0.03). CONCLUSIONS Older adults with CLBP have structural brain changes in the middle CC, middle cingulate WM, and the GM of the posterior parietal cortex as well as impaired attention and mental flexibility. Additional investigation is needed to corroborate and extend these findings and more clearly elucidate their relationship to physical function and the risk of disability.

Assessment of attention and memory efficiency in persons with solvent neurotoxicity

Memory and attention were evaluated in 40 persons with a history of organic solvent exposure and 40 demographically similar controls. Exposed subjects, in comparison to controls, had reduced digit spans, were deficient at learning new information, and recall on a Brown-Peterson distractor test was especially low following a 30-sec interference interval. If original learning was considered, long-term recall was similar for both groups. On a test of sustained attention, the Continuous Performance Test, exposed subjects became less accurate over successive blocks, a pattern opposite to that seen in control subjects. The data suggest that the memory impairment following solvent exposure may result from deficient allocation of attentional resources due to the inability to deal effectively with an increase in processing load.

Effects of Blood Lead Levels on Cognitive Function of Older Women

Elevated blood lead concentrations are known to have detrimental effects on neuropsychological function in both children and occupational cohorts of men and women. Although it is generally accepted that lead exposure at low levels is more dangerous for infants and children than for adults, the issue of the lowest level of exposure at which lead causes deleterious health effects in adults is yet to be solved. There is no available data on the role of lead exposure in cognitive dysfunction in nonoccupational cohorts of older persons. In the current study, we examined the cross-sectional relationship between blood lead levels and a variety of measures of neuropsychological function in a large cohort of elderly women recruited at both urban and rural sites. This study of elderly women demonstrates that blood lead levels as low as 8 micrograms/dl were significantly associated with poorer cognitive function as measured by certain neuropsychological tests. Even a slight decrement in cognition would have a large public health impact due to the large number of elderly at risk.

Risk factors associated with persistence of neuropsychological deficits in persons with organic solvent exposure

This study examined neuropsychological prognosis following organic solvent exposure. Twenty-seven persons with evidence of “mild toxic encephalopathy” were evaluated on two separate occasions with a standard neuropsychological test battery and the Minnesota Multiphasic Personality Inventory. Ratings by experienced clinicians revealed that 50% of exposed persons had improved neuropsychological performance at the second evaluation. The other 50% were rated as having no change or a decline in neuropsychological tests scores. While the majority of persons in the good-outcome group were working at the time of the follow-up evaluation, none of the persons in the poor-outcome group was actively employed. Persons rated as having shown no improvement were significantly more likely to have had a peak exposure—an episode in which they were briefly exposed to a larger than normal amount of solvent. In addition, persons in the poor outcome group reported higher levels of psychological distress, both initially and at the follow-up evaluation. Results from this study suggest that the presence of certain risk factors, namely a peak exposure and psychological distress, may be particularly detrimental for long-term neuropsychological outcome in persons with a history of organic solvent exposure.

Efficacy of percutaneous electrical nerve stimulation for the treatment of chronic low back pain in older adults.

OBJECTIVES: To determine the efficacy of a complementary analgesic modality, percutaneous electrical nerve stimulation (PENS), for the treatment of chronic low back pain (CLBP) in community‐dwelling older adults.