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Biomedical subjects

M L Voytko

Publications and source records attributed to M L Voytko.

24 records · Page 2Linked to original sources
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

Impairments in acquisition and reversals of two-choice discriminations by aged rhesus monkeys.

The ability to learn and perform reversals of two object, two patterns, and one spatial discrimination was examined in eight aged (28-34 years), and four adult (8-13 years) behaviorally naive monkeys. As a group, the aged monkeys demonstrated significant difficulties in learning and reversing some of the visual discrimination problems, but had no difficulty learning or reversing the spatial discrimination. Additional analyses revealed that an impairment in learning an object discrimination by the aged monkeys was characterized by a prolonged period of chance performance, and the impairments in performing visual discrimination reversals was related to difficulties in two distinct stages of reversal learning. Despite age-related differences, there was considerable variability in performance among the aged monkeys. These experiments provide the first evidence of significant impairments in learning and reversing visual discriminations by aged monkeys that have not had prior exposure to complex behavioral tasks.

Aging↗
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↗
PubMedDate not supplied

Neuronal number and size are preserved in the nucleus basalis of aged rhesus monkeys.

Neurons in the nucleus basalis of Meynert (NBM) were analyzed morphometrically in 21 rhesus monkeys ranging in age from 9 to 33 years. Numbers of cholinergic neurons were similar across all ages at several NBM levels in either Nissl-stained paraffin sections or sections processed immunocytochemically for nerve growth factor receptor (p75LNGFr). Size of NBM neurons was larger in aged monkeys than young monkeys at all NBM levels, particularly in the most posterior subdivision. A subset of monkeys were behaviorally characterized shortly before death, and partial correlation analyses indicated that increased age was associated with declines in recognition memory, visuospatial orientation, and reaction time. Controlling for age, spatial memory and concurrent discrimination abilities were associated with lower cell number in intermediate NBM. Numbers of neurons in anterior NBM did not correlate with any behavioral measure. These observations indicate that numbers of NBM cholinergic neurons are stable with age, that NBM neurons become hypertrophic in older animals, and that morphometric indices of cholinergic neurons are associated with cognitive function.

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