410 research outputs found
Evidence of a time constant associated with movement patterns in six mammalian species
Human psychophysical studies have provided evidence of a short duration time constant associated with perceptual tasks. This time constant is approximately 3 s in duration, and evidence suggests that it represents a central neural mechanism that functions to integrate "successive events into a Gestalt" in order to create a "subjective present." Recent studies have found a 3 s time constant in human and chimpanzee movement patterns, suggesting that a similar mechanism subserves both human perceptual and primate motor skills. These studies have focused exclusively on humans and chimpanzees; therefore, it is unclear whether this time constant represents a characteristic derived in the primate order or an ancestral characteristic found in many different mammalian orders. The current study looked for evidence of a 3 s time constant associated with movement patterns in six mammalian species representing three non-primate orders. The results showed that all six species' movement pattern event durations averaged about 3 s, and that there were no significant differences in the mean event durations among the species. Thus, the 3 s time constant originally found in human perceptual and primate motor skills is common among many mammalian orders and probably represents the operation of an ancestral neural mechanism.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/31468/1/0000390.pd
The interrelated effect of sleep and learning in dogs (Canis familiaris); an EEG and behavioural study
The active role of sleep in memory consolidation is still debated, and due to a large between-species variation, the investigation of a wide range of different animal species (besides humans and laboratory rodents) is necessary. The present study applied a fully non-invasive methodology to study sleep and memory in domestic dogs, a species proven to be a good model of human awake behaviours. Polysomnography recordings performed following a command learning task provide evidence that learning has an effect on dogs’ sleep EEG spectrum. Furthermore, spectral features of the EEG were related to post-sleep performance improvement. Testing an additional group of dogs in the command learning task revealed that sleep or awake activity during the retention interval has both short- and long-term effects. This is the first evidence to show that dogs’ human-analogue social learning skills might be related to sleep-dependent memory consolidation
A Model of Late Long-Term Potentiation Simulates Aspects of Memory Maintenance
Late long-term potentiation (L-LTP) appears essential for the formation of
long-term memory, with memories at least partly encoded by patterns of
strengthened synapses. How memories are preserved for months or years, despite
molecular turnover, is not well understood. Ongoing recurrent neuronal
activity, during memory recall or during sleep, has been hypothesized to
preferentially potentiate strong synapses, preserving memories. This hypothesis
has not been evaluated in the context of a mathematical model representing
biochemical pathways important for L-LTP. I incorporated ongoing activity into
two such models: a reduced model that represents some of the essential
biochemical processes, and a more detailed published model. The reduced model
represents synaptic tagging and gene induction intuitively, and the detailed
model adds activation of essential kinases by Ca. Ongoing activity was modeled
as continual brief elevations of [Ca]. In each model, two stable states of
synaptic weight resulted. Positive feedback between synaptic weight and the
amplitude of ongoing Ca transients underlies this bistability. A tetanic or
theta-burst stimulus switches a model synapse from a low weight to a high
weight stabilized by ongoing activity. Bistability was robust to parameter
variations. Simulations illustrated that prolonged decreased activity reset
synapses to low weights, suggesting a plausible forgetting mechanism. However,
episodic activity with shorter inactive intervals maintained strong synapses.
Both models support experimental predictions. Tests of these predictions are
expected to further understanding of how neuronal activity is coupled to
maintenance of synaptic strength.Comment: Accepted to PLoS One. 8 figures at en
The Biological Basis of a Universal Constraint on Color Naming: Cone Contrasts and the Two-Way Categorization of Colors
Many studies have provided evidence for the existence of universal constraints on color categorization or naming in various languages, but the biological basis of these constraints is unknown. A recent study of the pattern of color categorization across numerous languages has suggested that these patterns tend to avoid straddling a region in color space at or near the border between the English composite categories of “warm” and “cool”. This fault line in color space represents a fundamental constraint on color naming. Here we report that the two-way categorization along the fault line is correlated with the sign of the L- versus M-cone contrast of a stimulus color. Moreover, we found that the sign of the L-M cone contrast also accounted for the two-way clustering of the spatially distributed neural responses in small regions of the macaque primary visual cortex, visualized with optical imaging. These small regions correspond to the hue maps, where our previous study found a spatially organized representation of stimulus hue. Altogether, these results establish a direct link between a universal constraint on color naming and the cone-specific information that is represented in the primate early visual system
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