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Biomedical subjects

H A Buchtel

Publications and source records attributed to H A Buchtel.

At least 19 recordsLinked to original sources
PubMed1992

Verbal fluency and positron emission tomographic mapping of regional cerebral glucose metabolism.

Impairment in verbal fluency (VF) has been a consistently reported clinical feature of focal cerebral deficits in frontal and temporal regions. More recent behavioral activation studies with healthy control subjects using positron emission tomography (PET), however, have noted a negative correlation between performance on verbal fluency tasks and regional cortical activity. To see if this negative relationship extends to steady-state non-activation PET measures, thirty-three healthy adults were given a VF task within a day of their 18F-2-fluoro-2-deoxy-D-glucose PET scan. VF was found to correlate positively with left temporal cortical region metabolic activity but to correlate negatively with right and left frontal activity. VF was not correlated significantly with right temporal cortical metabolic activity. Some previous studies with normals using behavioral activation paradigms and PET have reported negative correlations between metabolic activity and cognitive performance similar to that reported here. An explanation for the disparate relationships that were observed between frontal and temporal brain areas and VF might be found in the mediation of different task demands by these separate locations, i.e., task planning and/or initiation by frontal regions and verbal memory by the left temporal area.

Adult↗
PubMed1990

Cerebral control of directed visual attention and orienting saccades.

The object of this experiment was to identify the contribution of the frontal and parietal lobes to the control of visual attention and voluntary saccades. A symbolic spatial cue (arrow) was used to indicate validly or invalidly the location of a visual target located to the left or right of the cue. Manual reaction time and reaction time to initiate a saccade to the target were measured. Patients with damage to the left frontal lobe (n = 6), right frontal lobe (n = 7) and right parietal lobe (n = 7) were compared with normal control subjects (n = 20). A sex difference was found for the right cerebral hemisphere patients in the manual reaction time data. Right parietal males and right frontal females showed an overall elevation in manual reaction time, reflecting an inability to maintain a normal level of visual arousal and/or motor activation. Conversely, right frontal males and right parietal females were not influenced significantly by cue validity, suggesting that they were unable to direct visual attention in a covert manner. All subjects showed a normal effect of cue validity on saccade reaction time. Thus the cortical areas studied do not appear to be necessary for directing visual attention with a saccade. Cue validity, however, affected saccade amplitude, especially in the left visual field of patients with right hemisphere damage. The cue validity effect depended both on the sex of the subject and the anterior/posterior location of damage in the right hemisphere. Damage to the right frontal lobe resulted in an 'under' reaction to the spatial cues, especially in the male patients. Saccades were smaller than normal following the valid cues, but larger than normal following the invalid cues. The effect was opposite following damage to the right parietal lobe. In this case, saccade amplitude reflected an 'over' reaction to the spatial cues, especially in the female patients. Saccades were larger than normal following valid cues and smaller than normal following invalid cues.

Analysis of Variance↗
PubMed1989

Spatial attentional shifts: further evidence for the role of polysensory mechanisms using visual and tactile stimuli.

Normal subjects performed simple reaction time responses to lateralized visual target stimuli (Experiment 1) and lateralized tactile target stimuli (Experiment 2). In each experiment, the lateralized targets were preceded at one of four intervals by a visual or tactile cue located on the same (valid cue), or opposite (invalid cue) side, or on both sides (neutral cue). The validity of the visual and tactile cues influenced the speed of response to either target stimulus. These findings, together with those previously reported (Buchtel and Butter, Neuropsychologia 26, 499-509, 1988), are consistent with the view that intra- and inter-modal spatial cueing is effective with modalities that are linked to orienting systems in which movements of the sensory array serve to improve sensory analysis.

Adult↗
PubMed1989

Auditory agnosia: apperceptive or associative disorder?

Neuropsychological testing of a patient with auditory agnosia showed that certain difficulties in the initial analysis of sounds may be the cause of his inability to understand spoken words and other sounds. Abnormalities included a slow reaction time to brief auditory stimuli (but not to equally brief visual stimuli or to longer auditory stimuli) and the need for approximately 1/4 sec of silence between two tones before the patient was able to hear them as separate. He could identify words and word associations if he was able to view the object whose name or word associate he was hearing. The findings imply that this patient's deficit in comprehending speech was probably apperceptive rather than associative in origin.

Agnosia↗
PubMed1988

Positron emission tomographic scan investigations of Huntington's disease: cerebral metabolic correlates of cognitive function.

Fifteen drug-free patients with early to mid-stage Huntington's disease (HD) were evaluated with positron emission tomographic (PET) scans of 18F-2-fluoro-2-deoxy-D-glucose uptake and quantitative measures of neurological function, learning, memory, and general intelligence. In comparison with a group of normal volunteers, the HD patients showed lower metabolism in both caudate (p less than 0.001) and putamen (p less than 0.001) on PET scans. A significant and positive relationship was found between neuropsychological measures of verbal learning and memory and caudate metabolism in the patient group but not in the normal group. Visual-spatial learning did not reflect a similar pattern, but performance intelligence quotient was positively related to both caudate and putamen metabolism in the HD group. Vocabulary level was unrelated to either brain structure. Discussion focuses on these and other observed brain-behavior relationships and on the implications of these findings for general behaviors such as those involved in coping and adaptation.

Adult↗
PubMed1988

Spatial attentional shifts: implications for the role of polysensory mechanisms.

Simple reaction times to lateralized visual (Experiment 1) or auditory (Experiment 2) targets were studied in normal subjects. The targets were preceded by a visual or auditory cue located on the same (valid cue), or opposite (invalid cue) side as the subsequent target, or on both sides (neutral cue), with one of four cue target intervals. The validity of visual and auditory cues influenced the speed of response to the visual target but not to the auditory target. It is hypothesized that cross-modal cueing of spatial position works only with modalities for which a movement (e.g. saccade) leads to improved sensory analysis.

Adult↗
PubMed1988

Long-lasting memory deficits in children recovered from Reye's syndrome.

Twenty-six children, ages 7-18 years, were tested for possible memory impairments following Reye's syndrome (RS). The RS group was matched to a normal control group on race, age, SES, and estimated IQ. The Wechsler Memory Scale (with delayed recall) and two depth-of-processing tests were administered. For the control group, the mean MQ-IQ difference was +2, while the MQ-IQ difference for the RS group was -14. This proved to be highly significant. Short-term memory and long-term memory scores were significantly lower for the RS group, with verbal memory tasks being most affected.

Adolescent↗
PubMed1979

The effect of hemidecortication on the inhibitory interactions in the superior colliculus of the cat.

Single neurons were recorded extracellularly from the superficial layers of the superior colliculus (SC) in 21 curarized cats. Four animals were normal unoperated cats, 17 were animals in which all cortical visual areas were ablated on one side from 7 to 69 days before the electrophysiological experiments. After cortical ablation all animals were blind in the visual field contralateral to the ablated side. In both normal and hemianopsic cats the effect of a visual stimulus located very far from the excitatory part of the unit receptive field, on the neuron responses to visual stimuli was studied. The remote stimulus (extra-field stimulus) was a hand moved black spot 10 degrees in diameter. In normal animals the introduction of the extra-field stimulus in the hemifield contralateral or ipsilateral to the recorded SC produced a marked reduction of unit responses to visual stimuli presented in their receptive field. This effect was particularly strong when the extra-field stimuli were introduced in the hemifield contralateral to the recorded side. In the hemianopsic animals the neurons of the SC ipsilateral to the lesion (receptive fields in the behaviorally blind hemifield) responded well to visual stimuli, but were only weakly inhibited by the extra-field stimuli presented in the blind hemifield. The neurons of this colliculus with the exception of those in the upper part of stratum griseum superficiale were normally inhibited by stimuli presented in the normal hemifield. The neurons of the SC contralateral to the lesion responded well to visual stimuli and were normally inhibited by stimuli presented in the normal hemifield; they were virtually not affected by stimuli presented in the blind hemifield. Mechanisms responsible for the abnormal inhibitory interactions between and within colliculi after cortical lesions and the possible behavioral implications of the findings are discussed.

Animals↗
PubMed1979

Cerebral hemispheric lateralization of cognitive deficits due to alcoholism.

Twenty chronic alcoholics and a group of matched control subjects were tested on verbal and visuospatial memory tasks in order to test directly the hypothesis that alcoholism disturbs cognitive functions subserved by the right hemisphere more than those subserved by the left hemisphere. The results provide some support for the hypothesis and indicate that information may be lost by pooling together test results from alcoholics which come from a mixture of verbal and nonverbal tasks.

Adult↗
PubMed1977

Hemispheric superiority in reaction time to faces: a sex difference.

In males but not females, reaction time to faces is faster when stimuli are presented to the right hemisphere than when presented to the left hemisphere. The complete lack of a hemispheric difference in females suggests that with brief exposure and immediate judgement, a lateralized mechanism specialized for faces can be activated only in males.

Dominance, Cerebral↗