Biomedical subjects

M L Voytko

Publications and source records attributed to M L Voytko.

5 recordsLinked to original sources

PubMed1991

Basal forebrain cholinergic system: a functional analysis.

This chapter has been organized empirically, focusing on the types of approaches that have been taken to understand BFCS function. This approach reflects the state of our knowledge about the behavioral and psychological functions of the BFCS. Considerable information has been gathered in the very short time that the BFCS has been the object of intense investigation. The results from the neurotoxic lesions and from the HACU studies provide some points of consistency and some puzzling differences. Both approaches to the study of basal forebrain function suggest that the MSA is involved in tasks that require spatial working memory; MSA lesions impaired choice accuracy, and HACU in the HIP was increased after performance. The pattern of results in simpler tasks is more difficult to interpret. In a left-right reference memory discrimination in a T-maze, MSA lesions did not impair acquisition or performance, whereas HACU in the HIP was activated during performance. This pattern of results suggests that although the MSA is engaged during this type of task, its activity is not necessary for normal performance. These, and other comparisons indicate the need for a systematic analysis of task demand (Olton, 1989b). Parametric manipulations of different task demands in a systematic fashion can indicate the extent to which the BFCS is involved in the function associated with each parametric manipulation. Ultimately, of course, the organization of this material should focus on particular psychological functions, rather than the techniques and procedures used to gather the information. Achieving this goal is going to require careful attention to the design of behavioral experiments so that definitive conclusions can be made about the extent to which the BFCS is involved in a given psychological function. A systematic application of task analysis can achieve this goal (Olton, 1986, 1989a, 1989b). For example, BFCS lesions in rats impair choice accuracy in spatial working memory tasks, and performance in these tasks engages the HACU system, at least in the HIP. If the spatial functions of this task involve the BFCS, then a nonspatial version of the task should produce a different pattern of results. If the spatial nature of the task is unimportant for BFCS function, then a nonspatial version of the task should produce the same results. By systematically changing one characteristic of the task at a time, the contribution of each component can be assessed.(ABSTRACT TRUNCATED AT 400 WORDS)

Acetylcholine↗

PubMed1987

The performance of visual tasks while segments of the inferotemporal cortex are suppressed by cold.

Cold was used to suppress the function of subdivisions of the inferotemporal cortex. Three cryodes were placed bilaterally, one over the lower bank of the superior temporal sulcus (sts), one over the middle temporal gyrus (mtg) and one over the inferior temporal gyrus (itg). The animals were tested with delayed match-to-sample (DMS) and simultaneous visual discriminations. The DMS required the animal to recall a projected image of an object over delays of 0, 15, 30 and 45 s. The 3 cryodes were cooled separately during the performance of the DMS and only itg cooling produced a deficit. This was compared to the effects of ablative bilateral lesions; damage to itg but not mtg disrupted performance of DMS. The greatest deficit was in an animal with a small lesion in the ventral pole and anterior extreme of itg. Cooling individual cryodes was without effect on a discrimination between horizontal and vertical stripes, but produced a significant deficit from each of the 3 placements on a discrimination between monkey faces. Chance performance on all visual discriminations resulted from cooling all cryodes. Unilateral cooling of all cryodes produced significant effects on the face discrimination, but there was no significant difference between the two sides in the severity of the deficit.

Animals↗

PubMed1986

Visual learning and retention examined with reversible cold lesions of the anterior temporal lobe.

Learning and retention of visual discriminations and delayed match-to-sample (DMS) performance were examined in monkeys while cooling the anterior temporal lobe. Four cryodes were bilaterally implanted on the dura overlying the anterior temporal cortex, an anterior pair covered the temporal pole (TP) and a posterior pair covered the anterior inferior temporal cortex (AIT). The visual discriminations were examined under 4 different test combinations of cooling and not cooling the anterior temporal lobe. Learning deficits were produced by cooling either TP or AIT. Once learned, there was no difficulty recalling discriminations under cooling or control conditions for either TP or AIT. There was a deficit during cooling in the recall of discriminations that had been learned prior to cooling TP or AIT. The animals were then trained and tested on a DMS task at a 0-s and 10-s delay. They performed at chance when either TP or AIT was cooled in the 0-s delay. Only TP was cooled at the 10-s delay and it also resulted in chance performance. The cold lesions demonstrated that the anterior temporal cortex, i.e. TP and AIT, has an important role in the processes of learning and, to a lesser extent, retention of visual information. The results also support previous findings regarding the participation of this area in DMS performance. The findings were discussed in relation to the amnesic syndrome.

Animals↗

PubMed1984

Visual learning suppressed by cooling the temporal pole.

Three monkeys were trained to remember colored photographs of objects over delays of 0, 15, 30, and 45 s. Then two pairs of cooling devices were implanted bilaterally over the anterior 9 mm of the temporal lobe. The devices consisted of 3 X 10 mm loops of stainless steel tubing into which cooled methanol could be pumped. One pair (anterior pair) covered the medial part of the temporal tip (area TG), starting at the rhinal sulcus and extending 3 mm laterally. The second pair (posterior pair) was placed 3 mm lateral to the anterior pair, covering the rest of TG and the anterior extreme of the inferotemporal gyri, anterior TE. Cooling either pair of probes produced a deficit at all delays, but the deficit was greater at the longest delays. There was no difference between cooling the anterior pair and cooling the posterior pair except that cooling the anterior pair greatly increased the disruption of recall that is produced by an interfering stimulus. When all four probes were cooled, which suppressed the function of the entire temporal tip, performance dropped to chance at all delays. While under this condition, the animals could not learn new visual discriminations but could perform previously learned visual discriminations. These results are consistent with the suggestion that the temporal pole is the store for the brief anterograde memory that is available to the medial temporal amnesics.

Animals↗

PubMedDate not supplied

Cholinergic immunoreactive fibers in monkey anterior temporal cortex.

Cholinergic processes in anterior temporal cortex of rhesus monkeys were identified using immunocytochemical techniques for ChAT. Labeled fibers were present throughout the temporal pole and anterior aspects of the superior temporal, middle temporal, and inferior temporal gyri. ChAT-immunoreactive fibers were most dense in layer I to superficial layer III throughout anterior temporal cortex. In temporal pole, agranular and dysgranular regions had a greater density of labeled fibers in superficial layers as compared to granular regions. In addition to the superficial concentration of cholinergic fibers in lateral temporal regions, numerous labeled fibers were also present in deep cortical layers in the inferior temporal gyrus of lateral temporal cortex, with lesser concentrations of immunoreactive fibers present in these layers in superior and middle temporal gyri. These patterns of cholinergic innervation may reflect the degree of cholinergic modulation of functions in anterior temporal cortex.

Animals↗