ONSET and OFFSET inhibitions: effect of increase and decrease of cue luminance on manual reaction time to a visual target.

Simple reaction time (RT) to a peripheral visual target is shortened when a non-informative cue is flashed at the target location 100-150 ms before target onset (early facilitation). With longer intervals, RT to targets appearing at cue hemifield is lengthened (inhibition of return). In the present study, we investigated these effects inverting the stimulus contrast in relation to background to see how these effects are related to the onset and/or to the offset of a cue darker or brighter than background. Ten subjects were asked not to respond to a non-informative cue (S1) appearing on a computer screen 6 degrees to the right or to the left of the center of a fixation cross (FP), but to respond, by pressing a microswitch, to a target (S2) occurring at 4 degrees from the FP in the same hemifield as S1 or in the opposite hemifield. There were two different types of sessions. In one, S1 and S2 were bright against a dark background and in the other, S1 and S2 were dark against a bright background. In each session there were two types of trials. In OFF trials, each trial began with the presentation of FP. Five hundred ms later, S1 appeared and remained on for 700 ms. S2 appeared 100 or 800 ms after the offset of S1. In ON trials, S1 onset occurred 1200 ms after the beginning of the trial and remained on until the end of trial. S2 appeared 100 or 800 ms after S1 onset.(ABSTRACT TRUNCATED AT 250 WORDS)

Onset and offset inhibitions: effect of increase and decrease of cue luminance on manual reaction time to a visual target

Simple reaction time (RT) to a peripheral visual target is shortened when a non-informative cue is flashed at the target location 100-150 ms before target onset (early facilitation). With longer intervals, RT to targets appearing at cue hemifield is lengthened (inhibition of return). In the present study, we investigated these effects inverting the stimulus contrast in relation to background to see how these effects are related to the onset and/or to the offset of a cue darker or brighter than background. Ten subjects were asked not to respond to a non-informative cue (S1) appearing on a computer screen 6§ to the right or to the left of the center of a fixation cross (FP), but to respond, by pressing a microswitch, to a target (S2) occurring at 4§ from the FP in the same hemifield as S1 or in the opposite hemifield. There were two different types of sessions. In one, S1 and S2 were bright against a dark background and in the other, S1 and S2 were dark against a bright background. In each session there were two types of trials. In OFF trials, each trial began with the presentation of FP. Five hundred ms later, S1 appeared and remained on for 700 ms. S2 appeared 100 or 800 ms after the offset of S1. In ON trials, S1 onset occurred 1200 ms after the beginning of the trial and remained on until the end of trial. S2 appeared 100 or 800 ms after S1 onset. When S2 onset followed S1 onset by 100 ms, RT to S2 occuring in the same hemifield did not differ from RT when S1 and S2 were in opposite hemifields. In contrast, after an S1-S2 interval of 800 ms, S1 onset elicited an inhibition of its hemifield. This inhibition was similar to that observed 100 ms or 800 ms after S1 offset. The same results were obtained if the cue and target were brighter or darker than the background, showing that the ONSET and OFFSET inhibitions are related not to cue luminance increase and decrease, respectively, but to the appearance and the disappearance of a salient stimulus in a homogeneous background. Moreover, these results suggest that ON and OFF channels of the visual system have similar effects on the orienting of attention

Aging and selective attention in arithmetic calculations.

The aim of the present work was to test the effect of aging on the capacity to perform and validate simple arithmetic calculations. Two experimental groups, eight young and eight old subjects, performed a set of three tasks (A,B,C), requiring different amounts of attentional resources. In test A, the subjects knew in advance the type of operation to be validated; in test B the subjects had to validate items of four randomly mixed operation types; in test C the subjects could use an informative cue which signalled in advance the kind of operation to be performed. The cue was true in 70% of items (valid trials) and false in 30% (invalid trials). The results confirmed a slowing down of cognitive processes in old people that partially depended on task complexity. Differently from young, old subjects could not use the informative cue to orient attention toward specific arithmetic facts: actually in test C the difference between invalid vs. valid trials does not reach statistical significance.

[Recall of the proper names of persons: effect of age and the modality of access]. / Rievocazione dei nomi propri di persona: effetto dell'eta' e della modalità di accesso.

Aging is associated with phenomena of slowing down of cognitive processes and impairment of neuropsychological performances. Elderly people also report difficulty in the retrieval of proper names. Verbal fluency (VF) tests are particularly effective for the identification of even slight mental impairments. In this experiment we utilized the usual tests of VF for semantic categories and letters of the alphabet together with three new tests of VF for first names, differing in mode of access. The first mode was free recall, the second mode was semantic (first names beginning with a particular letter), and the third mode was autobiographical (first names of relatives). There were 3 experimental groups: young people with high education level, elderly people with high education level and elderly people with low education level. The aim of our work was to verify whether aging modifies the performance in the VF tests, particularly in the three first name VF tests. No difference was found between the groups of young and elderly people with high education level. The comparison between the two groups of elderly people, with high and low education level, showed that significant differences were present in some but not in all of the VF tests. While the two groups clearly differed in semantically oriented tests, no difference could be detected in the test oriented to episodic memory. This result seems to be inconsistent with the hypothesis that aging affects mainly episodic memory.

[Effect of age on the orientation of attention: effect of changing the interval between signal and stimulus]. / Effetto dell'età sull'orientamento dell'attenzione: influenza delle variazioni dell'intervallo fra segnale e stimolo.

The purpose of the experiment was to examine the effect of aging on spatial attention. One of two possible locations, horizontally arranged, was cued. The subject had to respond to the onset of a visual stimulus, wherever it appeared. The task demand was to orient attention to the stimulated location before producing a response, or to reorient it if the position is not the cued one. Younger and older adults showed the same response pattern, despite the overall slowing down of response presented by the latter.

[Effects of age on orientation of attention]. / Effetti dell'età sull'orientamento dell'attenzione.

The present experiment investigated the influence of age on the magnitude of attentional effects. Subjects were cued to attend to one of two possible stimulus locations horizontally arranged. The instructions were to respond as fast as possible to the occurrence of a visual stimulus, regardless of whether it occurred in a cued or in a non-cued location. When the stimulus occurred in a non-cued location, the subject had to reorient attention to the non-attended, but stimulated, location. Reorienting of attention was directed toward either the left or the right side. The results showed that for the elders, time for reorienting was longer than for younger subjects.

Spontaneous activity of neurones of nucleus reticularis thalami in freely moving cats.

1. Fifty-four neurones of the caudal part of the nucleus reticularis thalami (nuc. ret.) were recorded during different phases of sleep and wakefulness in unanaesthetized freely moving cats.2. During wakefulness the activity of the neurones was characterized by a continuous, well-spaced discharge. The mean firing rate was 35.58 +/- 15.06 spikes/sec (average +/- S.D.).3. During sleep with synchronized e.e.g. (S-sleep) the neurones fired in high frequency bursts with long pauses in between. Each burst was formed of 10-15 spikes. Often the bursts were followed by prolonged discharges formed of spikes well spaced one from the other. Bursts followed by prolonged activity were more commonly observed at the beginning of S-sleep and during the S-sleep periods preceding sleep with desynchronized e.e.g., whereas bursts immediately followed by silence were more frequent in the S-sleep periods with e.e.g. delta waves. The long periods of silence between the bursts usually lasted over 200 msec and values greater than 1 sec were frequently found. The mean firing rate of neurones during S-sleep was 19.22 +/- 10.50 spikes/sec.4. During sleep with desynchronized e.e.g. (D-sleep) the activity of the neurones was, as during wakefulness, characterized by a continuous, well spaced, unclustered discharge. The mean firing rate was 40.00 +/- 18.74 spikes/sec. During the rapid eye movements of this phase most units increased the frequency of their discharge, which, nevertheless, maintained the unclustered feature proper to the desynchronized phase of sleep.5. Interspike interval distribution was similar during wakefulness and sleep with desynchronized e.e.g., whereas that for sleep with synchronized e.e.g. was markedly different from those for both the other stages.6. The implications of the striking similarity between the activity of reticularis neurones during wakefulness and sleep with desynchronized e.e.g. are discussed.