Long-term memory formation in the chick requires mobilization of ryanodine-sensitive intracellular calcium stores

Training chicks (Gallus domesticus) on a one-trial passive avoidance task results in transient and time-dependent enhanced increases in N-methyl-d-aspartate- or alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate-stimulated intracellular calcium concentration in synaptoneurosomes isolated from a specific forebrain region, the intermediate medial hyperstriatum ventrale. This increase could result from either calcium entry from the extracellular medium or from mobilization of intracellular calcium stores. We have therefore examined the effects of dantrolene, an inhibitor of calcium release from the intracellular ryanodine-sensitive store, on these processes. Dantrolene, 50 nmol per hemisphere injected intracerebrally 30 min pre- or 30 min posttraining, blocked longer term memory for the passive avoidance task, whereas memory for the task was unaffected when dantrolene was injected at earlier or later times. Preincubation of synaptoneurosomes, isolated from the intermediate hyperstriatum ventrale 10 min after training, with 100 nM dantrolene abolished the enhanced training-induced increase in intracellular calcium concentration elicited by 0.5 mM N-methyl-d-aspartate. By contrast, the training-induced enhancement of the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate-stimulated increase in intracellular calcium concentration in synaptoneurosomes prepared 6 h posttraining was unaffected by preincubation with dantrolene, which was not amnestic at this time. Calcium release from ryanodine-sensitive intracellular stores may thus be a necessary stage in the early phase of the molecular cascade leading to the synaptic modulation required for long-term memory storage.     

Sex differences in perception of temporal order

On duration judgments lasting seconds to minutes, which are thought to be cognitively mediated, women typically perceive time intervals as longer than men do. On a perceptual level in the milliseconds range, few reports indicate higher acuity of temporal processing in men than in women. In this study, sex differences in the perception of temporal order of two acoustic stimuli were identified in neurologically healthy subjects, as well as in brain-injured patients with lesions in either the left or the right hemisphere. Women needed longer interstimulus intervals than men before they were able to indicate the correct temporal order of two clicks. Neurobiological evidence and findings on cognitive strategies are discussed to explain the apparent psychophysical sex differences.     

Differential involvement of mGluR1 and mGluR5 in memory reconsolidation and retrieval in a passive avoidance task in 1-day old chicks

Group I metabotropic glutamate receptors (mGluRs) are involved in memory formation. The Ca2+ signal derived from stimulation of IP3 receptors (IP3Rs) via mGluRs, initiates protein synthesis that is required for memory consolidation and reconsolidation. However it has been suggested that different mechanisms are triggered by mGluR1/5 activation in these two processes. It is also not clear whether the transient amnesia observed after blockade of group I mGluRs after a reminder, results from disturbance of memory reconsolidation or temporal impairment of recall. The aim of this study was to examine more closely the role of mGluR1 in memory consolidation and reconsolidation and to detect differences in the participation of mGluR1 and mGluR5 in memory retrieval after initial training and after the remainder of the task. Our results demonstrate, that in chicks performing a one-trial passive avoidance task, antagonists of mGluR1, mGluR5 and IP3R significantly disturb memory consolidation and reconsolidation. Inhibition of mGluR5 and IP3R also impairs memory recall, whereas mGluR1 do not seem to participate in this process. The presented data suggest that activation of mGluR1 and mGluR5 is necessary for the correct course of memory consolidation and reconsolidation, whereas mGluR5 are additionally involved in retrieval processes dependent on Ca2+ release from IP3 activated intracellular stores.     

Political Conservatism,Need for Cognitive Closure,and Intergroup Hostility

Two studies examined the interaction of political conservatism and the need for cognitive closure in predicting aggressiveness in intergroup conflict and hostility toward outgroups. In the first study, Polish participants indicated their preference for coercive conflict strategies in the context of a real‐life intergroup conflict. Only among participants who identify themselves as conservative, need for cognitive closure was positively and significantly related to preference for aggressive actions against the outgroup. In the second study, the predicted interaction was investigated in the context of the terrorist threat in Poland. The findings indicated that high in need for closure conservatives showed greater hostility against Arabs and Muslims only when they believed that Poland was under threat of terrorist attacks inspired by Islamist fundamentalism.     

Temporal order perception of auditory stimuli is selectively modified by tonal and non-tonal language environments

The close relationship between temporal perception and speech processing is well established. The present study focused on the specific question whether the speech environment could influence temporal order perception in subjects whose language backgrounds are distinctively different, i.e., Chinese (tonal language) vs. Polish (non-tonal language). Temporal order thresholds were measured for both monaurally presented clicks and binaurally presented tone pairs. Whereas the click experiment showed similar order thresholds for the two language groups, the experiment with tone pairs resulted in different observations: while Chinese demonstrated better performance in discriminating the temporal order of two “close frequency” tone pairs (600 Hz and 1200 Hz), Polish subjects showed a reversed pattern, i.e., better performance for “distant frequency” tone pairs (400 Hz and 3000 Hz). These results indicate on the one hand a common temporal mechanism for perceiving the order of two monaurally presented stimuli, and on the other hand neuronal plasticity for perceiving the order of frequency-related auditory stimuli. We conclude that the auditory brain is modified with respect to temporal processing by long-term exposure to a tonal or a non-tonal language. As a consequence of such an exposure different cognitive modes of operation (analytic vs. holistic) are selected: the analytic mode is adopted for “distant frequency” tone pairs in Chinese and for “close frequency” tone pairs in Polish subjects, whereas the holistic mode is selected for “close frequency” tone pairs in Chinese and for “distant frequency” tone pairs in Polish subjects, reflecting a double dissociation of function.     

Duration processing in children as determined by time reproduction: implications for a few seconds temporal window

From research carried out over recent years using different experimental paradigms, it has become apparent that central information processing is temporally segmented into sequential units of a few seconds. This segmentation presumably reflects a neuronal process of temporal integration (TI) which automatically binds successive events into temporal units. Support for such TI comes, for example, from studies on temporal reproduction where standards up to approximately 2-3 s are reproduced veridically. Using this paradigm of temporal reproduction, we investigated the effect of normal cognitive development of sensory modality and of the range of presented standards on TI. Sixty children aged 6-7, 9-10 and 13-14 years reproduced visual or auditory standard durations ranged from 1 to 5.5 s or from 1 to 3 s. The results showed that durations of approximately 2 s were reproduced correctly, whereas those longer than 2.5 s were under-reproduced in the three age groups. For standards shorter than 2 s substantial age-related differences were revealed: the youngest group displayed significant over-reproduction comparing to older subjects. These observations indicate that the upper limit for TI is a stable feature across the different age groups. Furthermore an age-related modulation within the temporal window of the operating TI seems to be linked to cognitive development.