Biomedical subjects

A Belger

Publications and source records attributed to A Belger.

6 recordsLinked to original sources

PubMed1992

Interhemispheric interaction affected by computational complexity.

The present study investigated whether dividing information between the hemispheres becomes more advantageous to task performance as computational complexity increases. We hypothesized that interhemispheric processing would benefit performance especially for computationally complex tasks, whereas it would hinder performance for relatively simple ones. A letter-matching task was given to 23 subjects at three levels of computational complexity. Complexity was varied either by increasing the number of inputs to be processed or by the nature of the decision to be made. The results indicated that each of these manipulations of complexity influenced performance by making it more advantageous to have both hemispheres involved in processing rather than just one. Furthermore, the effects of each manipulation were separable.

Adolescent↗

PubMed1991

Inter-versus intrahemispheric concordance of judgments in a nonexplicit memory task.

Performance for explicit probed recollection of an item's presentation is usually superior when initial presentation and probe are directed to the same hemisphere than when they are directed to opposite hemispheres. The present study explored whether a same-hemisphere advantage could also be observed for a nonexplicit memory task by examining concordance for initial and subsequent ratings of line length. Results indicated that mean ratings of line length differed less between initial and subsequent presentation when the lines were viewed in the same rather than opposite visual fields. This finding held even though mean ratings for initial presentation of items in the right and left visual fields did not differ. These findings suggest that the same-hemisphere advantage is a relatively basic characteristic of memorial processing in the hemispheres.

Adult↗

PubMed1991

Effects of acute aspartame and acute alcohol ingestion upon the cognitive performance of pilots.

Anecdotal evidence has associated the artificial sweetener aspartame with a number of symptoms of central nervous system (CNS) dysfunction. There are, however, little scientific data concerning the effect of aspartame upon complex mental operations such as those necessary for flying an aircraft. Thirteen pilots were tested in a double-blind study using the SPARTANS cognitive test battery of aviation-relevant information-processing tasks. These tasks relate to perceptual-motor abilities, spatial abilities, working memory, attentional performance, risk taking, processing flexibility, planning and sequencing ability. Subjects were tested over five sessions consisting of pretest and posttest controls and three randomly ordered treatment sessions. The treatment conditions involved an aspartame dose of 50 mg/kg body weight, a placebo condition, and an ethyl alcohol (0.1% BAL) condition as the positive control. No detectable performance decrements were associated with the aspartame condition, although decrements in psychomotor and spatial abilities were detected in the ethanol condition. Results were found to be consistent with prior flight-simulator studies of alcohol, but do not appear to support the concerns expressed in anecdotal testimony regarding the deleterious effects of aspartame upon cognitive performance.

Aerospace Medicine↗

PubMed1990

Interhemispheric interaction: how do the hemispheres divide and conquer a task?

The present studies investigated how dividing processing between the hemispheres affects task performance. In particular, they examined whether dividing processing between the hemispheres leads to a performance advantage only when task demands exceed a certain threshold. In Experiment 1 processing demands were manipulated by varying the difficulty of the decision process. In the more difficult task, subjects decided as quickly as possible whether two of three letters had the same name (e.g. A a), whereas in the less difficult task they simply decided whether two of the three were physically identical (e.g. A A). As expected, dividing processing between the hemispheres aided performance for the more difficult name-identity task whereas it actually hindered performance for easier physical-identity task. In Experiment 2, subjects made a physical-identity decision about a different stimulus, digits. The pattern of results found in Experiment 1 for the physical-identity task was replicated; interhemispheric processing hindered task performance. These results indicate that the physical characteristics of a stimulus have minimal influence on the extent to which interhemispheric processing aids task performance. In Experiment 3, subjects were required to make more difficult decisions about digits. In one task, they decided whether the sum of two of the three digits was greater than or equal to 10, and in the other they decided if the value of a particular digit was less than either of the other two. Dividing processing between the hemispheres led to faster performance for both tasks, similar to the results for the name-identity condition. In sum, these experiments suggest that when task requirements are demanding, performance is enhanced by distributing processing across the hemispheres.

Adult↗

PubMed1990

Interhemispheric processing in left- and right-handers.

Inter- and intrahemispheric processing for left- and right-handers were compared in two experiments. In one, subjects performed a digit-matching task and in the other they decided if two letters were part of a previously presented word. On some trials the matching items were presented initially only to one hemisphere (within-hemisphere trials), and hence the match decision could be reached by a hemisphere in isolation. On other trials, one item of the match pair was presented to each hemisphere (across-hemisphere trials), requiring interhemispheric interaction for the match decision. Patterns of performance on within-as compared to across-hemisphere trials were identical for the two handedness groups in both experiments. Furthermore, individual characteristics of subjects such as their hand posture, sex and family history of left-handedness did not affect the pattern of performance. These results suggest that interhemispheric processing may not differ between right- and left-handers.

Brain↗

PubMedDate not supplied

Human extrastriate visual cortex and the perception of faces, words, numbers, and colors.

Electrophysiological correlates of the processing of visual information were studied in epileptic patients with electrodes chronically implanted on the surface of striate and extrastriate cortex. In separate experiments patients viewed faces, letter strings (words and non-words), numbers, and control stimuli. A negative potential, N200, was evoked by faces, letter strings, and numbers, but not by the control stimuli. N200 was recorded bilaterally from discrete regions of the fusiform and inferior temporal gyri. These category-specific face, letter-string, and number "modules" vary in location. In most cases there was no overlap in the location of face and letter-string modules, suggesting a mosaic of functionally discrete regions. In some cases letter-string and number N200s were recorded from the same location, suggesting that these modules may be less spatially and functionally discrete. Face N200-like potentials can be recorded from temporal scalp, allowing the possibility of studying early face processing in normal subjects. Longer-latency face-specific potentials were recorded from the inferior surface of the anterior temporal lobe. Potentials evoked by colored checkerboards were recorded from a region of the fusiform gyrus posterior to the fusiform region from which category-specific N200s were recorded. These results suggest that there are several processing streams in inferior extrastriate cortex. In addition to object recognition systems previously proposed for faces and words, our preliminary results suggest a separate system dealing with numbers. Postulated systems dealing with larger manipulable objects and animals have not been detected.

Color Perception↗