Role Of Visual Memory Research Articles

Association between cross-dominance and visual memory - A cross-sectional study

Background: Ocular dominance plays an important role in visual memory. Although many studies are done to find the relationship between cross-dominance and their performance in sports, little was known about the effect of cross-dominance in visual memory. Aim and Objective: The present study was aimed to find if there exists an association between cross-dominance and visual memory. Materials and Methods: In this study, 40 above average subjects in the age group 18–30 years of both genders with cross-dominance is taken as study group and 40 above average subjects with complete lateral dominance who are age and sex matched is taken as control. A detailed history of the subjects was collected and they are subjected to complete ophthalmological and neurological examination to rule out any neurological deficits. Dominant eye was found using miles test and visual memory was evaluated using Benton’s visual retention test. Results: In this study, it was found that though cross dominant subjects had less score than complete lateral dominant subjects, the difference is statistically insignificant. Conclusion: There is no significant difference in visual memory between the complete lateral dominance and cross dominant subjects.

Identification of distinct tyraminergic and octopaminergic neurons innervating the central complex of the desert locust, Schistocerca gregaria

The central complex is a group of modular neuropils in the insect brain with a key role in visual memory, spatial orientation, and motor control. In desert locusts the neurochemical organization of the central complex has been investigated in detail, including the distribution of dopamine-, serotonin-, and histamine-immunoreactive neurons. In the present study we identified neurons immunoreactive with antisera against octopamine, tyramine, and the enzymes required for their synthesis, tyrosine decarboxylase (TDC) and tyramine β-hydroxylase (TBH). Octopamine- and tyramine immunostaining in the central complex differed strikingly. In each brain hemisphere tyramine immunostaining was found in four neurons innervating the noduli, 12-15 tangential neurons of the protocerebral bridge, and about 17 neurons that supplied the anterior lip region and parts of the central body. In contrast, octopamine immunostaining was present in two bilateral pairs of ascending fibers innervating the upper division of the central body and a single pair of neurons with somata near the esophageal foramen that gave rise to arborizations in the protocerebral bridge. Immunostaining for TDC, the enzyme converting tyrosine to tyramine, combined the patterns seen with the tyramine- and octopamine antisera. Immunostaining for TBH, the enzyme converting tyramine to octopamine, in contrast, was strikingly similar to octopamine immunolabeling. We conclude that tyramine and octopamine act as neurotransmitters/modulators in distinct sets of neurons of the locust central complex with TBH likely being the rate-limiting enzyme for octopamine synthesis in a small subpopulation of TDC-containing neurons.

Characterization of Lobula Giant Neurons Responsive to Visual Stimuli That Elicit Escape Behaviors in the CrabChasmagnathus

In the grapsid crab Chasmagnathus, a visual danger stimulus elicits a strong escape response that diminishes rapidly on stimulus repetition. This behavioral modification can persist for several days as a result of the formation of an associative memory. We have previously shown that a generic group of large motion-sensitive neurons from the lobula of the crab respond to visual stimuli and accurately reflect the escape performance. Additional evidence indicates that these neurons play a key role in visual memory and in the decision to initiate an escape. Although early studies recognized that the group of lobula giant (LG) neurons consisted of different classes of motion-sensitive cells, a distinction between these classes has been lacking. Here, we recorded in vivo the responses of individual LG neurons to a wide range of visual stimuli presented in different segments of the animal's visual field. Physiological characterizations were followed by intracellular dye injections, which permitted comparison of the functional and morphological features of each cell. All LG neurons consisted of large tangential arborizations in the lobula with axons projecting toward the midbrain. Functionally, these cells proved to be more sensitive to single objects than to flow field motion. Despite these commonalities, clear differences in morphology and physiology allowed us to identify four distinct classes of LG neurons. These results will permit analysis of the role of each neuronal type for visually guided behaviors and will allow us to address specific questions on the neuronal plasticity of LGs that underlie the well-recognized memory model of the crab.

COMT and neurocognition: New evidence for a role in visual memory

COMT and neurocognition: New evidence for a role in visual memory

Long-term modifications of synaptic efficacy in the human inferior and middle temporal cortex.

The primate temporal cortex has been demonstrated to play an important role in visual memory and pattern recognition. It is of particular interest to investigate whether activity-dependent modification of synaptic efficacy, a presumptive mechanism for learning and memory, is present in this cortical region. Here we address this issue by examining the induction of synaptic plasticity in surgically resected human inferior and middle temporal cortex. The results show that synaptic strength in the human temporal cortex could undergo bidirectional modifications, depending on the pattern of conditioning stimulation. High frequency stimulation (100 or 40 Hz) in layer IV induced long-term potentiation (LTP) of both intracellular excitatory postsynaptic potentials and evoked field potentials in layers II/III. The LTP induced by 100 Hz tetanus was blocked by 50-100 microM DL-2-amino-5-phosphonovaleric acid, suggesting that N-methyl-D-aspartate receptors were responsible for its induction. Long-term depression (LTD) was elicited by prolonged low frequency stimulation (1 Hz, 15 min). It was reduced, but not completely blocked, by DL-2-amino-5-phosphonovaleric acid, implying that some other mechanisms in addition to N-methyl-DL-aspartate receptors were involved in LTD induction. LTD was input-specific, i.e., low frequency stimulation of one pathway produced LTD of synaptic transmission in that pathway only. Finally, the LTP and LTD could reverse each other, suggesting that they can act cooperatively to modify the functional state of cortical network. These results suggest that LTP and LTD are possible mechanisms for the visual memory and pattern recognition functions performed in the human temporal cortex.

The role of visual memory in the assessment of Turner syndrome: A case study

The role of visual memory in the assessment of Turner syndrome: A case study

Uncinate fascicle section leaves delayed matching-to-sample intact, with both large and small stimulus sets.

An earlier study found that rhinal cortex ablations in the monkey (Macaca fascicularis) impaired delayed matching-to-sample only when the stimuli in the experiment came from a large population of possible stimuli, not when the stimulus population was small. The present experiment tested the idea that delayed matching-to-sample with a small stimulus population selectively engages the direct projection from visual association cortex to the prefrontal cortex, bypassing the rhinal cortex. This selective involvement could explain the preservation, after rhinal cortex ablations, of memory for items drawn from a small stimulus population. We trained monkeys preoperatively in delayed matching-to-sample with large and small stimulus populations, exactly as in the earlier study, then examined the effect of sectioning the cortico-cortical pathway between visual association cortex and prefrontal cortex, the uncinate fascicle. Uncinate fascicle section had no effect on postoperative performance of delayed matching-to-sample, with either large or small stimulus populations. These data give no support to the idea that preserved matching with a small stimulus population after rhinal lesions reflects the selective involvement in this task of the direct projection from visual association cortex to prefrontal cortex. Further, they strengthen the idea (derived from earlier studies of uncinate fascicle section) that the uncinate fascicle does not play a general role in visual memory or perception, but instead has a specialized function in the processing of conditional instruction cues.

Activity of neurons in anterior inferior temporal cortex during a short- term memory task

Inferior temporal (IT) cortex of primates is known to play an important role in visual memory. Previous studies of IT neurons during performance of working memory tasks have found modulation of responses when a current stimulus matched an item in memory; however, this effect was lost if other stimuli intervened in the retention interval. To examine how IT cortex retains memories while new stimuli are activating the cells, we recorded from IT neurons while monkeys performed a delayed matching-to-sample task, with multiple intervening items between the sample and matching test stimulus. About half of the cells responded differently to a test stimulus if it matched the sample, and this difference was maintained following intervening stimuli. For most of the affected cells, the responses to matching stimuli were suppressed; however, for a few cells the opposite effect was seen. Temporal contiguity alone could not explain the results, as there was no modulation of responses when a stimulus on one trial was repeated on the next trial. Thus, an active reset mechanism appears to restrict the memory comparison to just the stimuli presented within a trial. The suppressive effects appear to be generated within or before IT cortex since the suppression of response to matching stimuli began almost immediately with the onset of the visual response. The memory of the sample stimulus affected not only the responses to matching stimuli but also those to nonmatching stimuli. There was suggestive evidence that the more similar a nonmatching stimulus to the sample, the more the response was suppressed. About a quarter of the cells showed stimulus-selective activity in the delay interval following the sample. However, this activity appeared to be eliminated by intervening stimuli. Thus, it is unlikely that delay-interval activity in IT contributed to the performance of this particular version of delayed matching to sample. To determine how much information about the match-nonmatch status of the stimulus was conveyed by individual neurons, we analyzed the responses with discriminant analysis. The responses of an individual IT neuron could be used to classify a stimulus as matching or nonmatching on about 60% of the trials. To achieve the same performance as the animal would require averaging the responses of a minimum of 25 IT neurons. There was no evidence that mnemonic information was carried by temporal variations in the spike trains. By contrast, there was a modest amount of temporal variation in sensory responses to different visual stimuli.(ABSTRACT TRUNCATED AT 400 WORDS)

Scopolamine affects short-term memory but not inferior temporal neurons.

Effects of scopolamine on performance of a delayed matching-to-sample task and on the properties of neurons in anterior-ventral inferior temporal (IT) cortex were examined in two monkeys. Both monkeys were impaired on the task after systemic administration of scopolamine, suggesting that scopolamine disrupts recency memory. Despite the behavioral deficit, neurons in IT cortex, a region having an important role in visual memory and neuronal properties consistent with that role, were largely unaffected by scopolamine. This dissociation between the behavioral and neuronal effects of scopolamine indicates that the drug either acts at a different site or disrupts unobserved mechanisms at the IT site.