Background: The chronic stress of social isolation is a valid predictor of cognitive pathology. This study aimed to compare the effects of long-term social isolation on female versus male Wistar rats’ learning and memory. We hypothesized that prolonged social isolation stress, which starts early in life, would affect learning in a sex-dependent manner. Methods: Social isolation started at the edge of early to mid-adolescence and lasted 9 months. The rat’s cognitive abilities were assessed by habituation and reactivity to novelty in the open field (OF) test, spatial memory in the Morris water maze (MWM), and the conditioned passive avoidance (PA) reflex. Basal serum corticosterone levels were assessed using an enzyme-linked immunosorbent assay. Results: Regardless of the housing conditions, females habituated to the OF under low illumination slower than males. Under bright light, the single-housed rats showed hyporeactivity to novelty. In the MWM, all the rats learned to locate the platform; however, on the first training day, the single-housed females’ speed was lower relative to other groups. Four months later, in the post-reminder probe trial, the single-housed rats reached the area around the platform site later, and only males, regardless of housing conditions, preferred the target quadrant. Single-housed rats, irrespective of sex, showed a PA deficit. There was a more pronounced conditioned fear in the single-housed males than in females. In both male and female rats, basal corticosterone levels in rat blood serum after 9 months of social isolation did not differ from that in the group-housed rats of the corresponding sex. Meanwhile, females’ basal corticosterone level was higher than in males, regardless of the housing conditions. The relative weight of the adrenal glands was increased only in single-housed females. Conclusions: Under long-term social isolation, started early in life, single-housed females compared with males showed more pronounced cognitive impairments in the MWM and PA paradigm, findings that specify their greater vulnerability to the stress of prolonged social isolation.

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Background. The Tip-Of-the-Tongue (TOT) state occurs when a person fails to retrieve a familiar word, e.g., a name, from long-term memory, while knowing perfectly well that the forgotten word exists in memory and being able to report some information about it (semantic associations, the first letter, the number of syllables, etc.).objective and method. In the present work, we studied the activation of brain structures during the TOT state. The participants (N = 20; age 21.5 ± 4.1) viewed portraits of movie stars whose names they were asked to remember. Event related potentials (ERP) were registered in three conditions: 1) the participant remembered the name; 2) the participant did not know the name; 3) the participant knew the name but could not remember it (TOT-state). The sources of cortical activation were computed (dSPM algorithm).Results. Time intervals demonstrating significant differences (t-test) in activation among the three conditions were calculated for each activated area, so that up to four different stages of processing could be delineated. According to our analysis, face perception involves activation of the visual cortex (left cuneus and right precuneus cortices), banks of the superior temporal sulci, poles of frontal and temporal lobes, and fusiform gyrus. The early activation does not depend on the successful retrieval of the name. A second increase in activation of the visual cortex is present at a later stage of processing, when name retrieval fails or if it is impeded.conclusion. We have shown that successful face recognition involves activation of the posterior cingulate cortex and the isthmus of the cingulate cortex in both hemispheres. Additionally, the parahippocampal gyrus is less active at the early stages and more active at the later stages of processing in the TOT-state, when name retrieval from the long-term memory fails.

Response inhibition one of the crucial cognitive functions in humans. Neuroimaging studies revealed the critical role of the right presupplementary motor area and the right anterior cingulate cortex in response inhibition. These data were obtained mostly on right-handers; however, lateralization of this function could be related to manual lateral asymmetry in humans. We compared brain areas involved in simple response inhibition tasks performance (rings and letters were used as visual stimuli) and differences in the activated brain structures between groups of participants with different types of motor asymmetry by fMRI. 29 participants (23 right-handers and 6 left-handers) performed Go/NoGo task and Stop-signal task. In Go/NoGo task the participants had to ignore specific non-verbal stimuli (red rings). In Stop-signal task the participants had to ignore specific verbal stimuli (red letters). Results showed increased activation of the right cerebellar hemisphere only for right-handers in comparison with lefthanders in Stop-signal task. Within-group analysis in the left-handers group revealed activation of the fusiform gyrus and the BA19 during Go/NoGo task in comparison with Stop-signal task. Significant differences have been demonstrated between right-handers and left-handers in simple response inhibition tasks which involve verbal stimuli processing. The right cerebellum structures have been activated during verbal information processing in right-handers in Stop-signal-task.