The cell populations of the occipital cortex were examined in young rats subjected to different sensory experiences. In one series recently weaned animals were reared in enriched, impoverished or control environments. The enriched environment was obtained by keeping the animals among "toys" and other rats; the impoverished environment, by rearing the animals one per cage in a darkened, quiet room; and the control environment, by housing the animals three per cage under usual animal room conditions. Six recently weaned rats were kept in each environment for 30 days and ten, for 80 days. In a second series suckling rats were handled daily. Handling consisted of touching, holding and rubbing rat pups for 15 minutes per day during the first ten days after birth; twelve rats were studied, six handled and six unhandled controls. In the two series, the animals were sacrificed under anesthesia by perfusion with mixed aldehydes. Semithin epon sections of occipital cortex were stained with toluidine blue; neurons and the three main types of glia were enumerated. In addition, the thickness of the cortex was measured and the glial cells of corpus callosum counted in the animals exposed to the three environments for 80 days. Under the influence of the enriched environment, the occipital cortex enlarged, the number of oligodendrocytes increased over the controls by 27-33% in the 30- and 80-day groups and the number of astrocytes, by 13% in the 80-day group. Within the cortex, only certain layers showed the increase in glial numbers. In the corpus callosum, however, the numbers of glial cells did not differ from those in controls. In the animals exposed to the impoverished environment, neither the size of the cortex nor the number of oligodendrocytes and astrocytes differed from controls. The animals subjected to handling also showed evidence of cortical enlargement, but the only significant change in glial cells was a 12% increase in astrocytes. It is concluded that handling and enrichment produce changes in anatomical indices of neural function including depth of cortex and numbers of glial cells. The glial response was specific to the type.of manipulation since astrocytes were predominantly affected by handling and oligodendrocytes, by enrichment. The effect of handling on astrocytes may be attributed to the stimulation being applied at a time of astrocyte proliferation, whereas the effect of enriched environment on oligodendrocytes occurred at a time of active production of these cells. The differences in cell numbers were explained by changes in the rate of cell population growth; since the impoverished did not differ from the control animals, the changes probably consisted of growth acceleration in the enriched animals rather than diminution in the impoverished ones.

Experiments were conducted to test the impact of embedding mental action verbs within instructions. Experiment 1 examined the instructional effects of these verbs on response time to a visual stimulus. Significant response time differences resulted from instructing participants to engage in different mental actions. Using Multidimensional Scaling, Experiment 2 explored how people understand the relationships amongst mental action verbs, resulting in a single "level of processing" dimension. Experiment 3 was designed to further explore the relationship of these verbs to cognition and behaviour. Signal detection analysis was used to determine if participants were shifting their criterion depending on the level of processing suggested in the instruction. Results showed an effect of instruction on response time, but not on criterion, sensitivity, or accuracy. Response time effects were found that were consistent with differences in word characteristics, including meaning.

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Dickinson and Szeligo (Can J Exp Psychol 62(4):211-222, 2008) found that processing time for simple visual stimuli was affected by the visual action participants had been instructed to perform on these stimuli (e.g., see, distinguish). It was concluded that these effects reflected the differences in the durations of these various visual actions, and the results were compared to participants' subjective ratings of word meaning but it was also possible that word characteristics like length might have influenced response times. The present study takes advantage of word length differences between French and English visual action words in order to address this issue. The goals of the present study were to provide evidence that (1) the processing time differences previously found were due to differences in the cognitive actions represented by these words (and not due to characteristics to the words themselves), and (2) that individuals subjectively differentiate visual action words in such a way that allows for predictable differences in behaviour. Participants differentiated 14 French visual action words along two dimensions. Four of these words were then used in the instructions for a size-discrimination task. Processing time depended on the visual action word in the instruction to the task and differed in a predictable manner according to word meaning but not word length.