Spreading activation in emotional memory networks and the cumulative effects of somatic markers.

The theory of spreading activation proposes that the activation of a semantic memory node may spread along bidirectional associative links to other related nodes. Although this theory was originally proposed to explain semantic memory networks, a similar process may be said to exist with episodic or emotional memory networks. The Somatic Marker hypothesis proposes that remembering an emotional memory activates the somatic sensations associated with the memory. An integration of these two models suggests that as spreading activation in emotional memory networks increases, a greater number of associated somatic markers would become activated. This process would then result in greater changes in physiological functioning. We sought to investigate this possibility by having subjects recall words associated with sad and happy memories, in addition to a neutral condition. The average ages of the memories and the number of word memories recalled were then correlated with measures of heart rate and skin conductance. The results indicated significant positive correlations between the number of happy word memories and heart rate (r = .384, p = .022) and between the average ages of the sad memories and skin conductance (r = .556, p = .001). Unexpectedly, a significant negative relationship was found between the number of happy word memories and skin conductance (r = -.373, p = .025). The results provide partial support for our hypothesis, indicating that increasing spreading activation in emotional memory networks activates an increasing number of somatic markers and this is then reflected in greater physiological activity at the time of recalling the memories.

Spatial configuration of vertically related word pairs modulates the N400 component.

This study examined the effect of spatial iconicity on the N400 component. Spatial iconicity is defined as the spatial arrangement of words on a screen relative to the spatial arrangement of their referents (e.g. attic-basement). In two experiments, electroencephalograms were recorded in 32 participants while performing a semantic relatedness judgment task on pairs of words that were either related or unrelated. All of the related word pairs were parts of objects that shared a vertical spatial relationship. In Experiment 1, the words of each pair were presented simultaneously on top of one another. Results showed that related word pairs presented in a spatial arrangement that mismatched the spatial relationship of their referents were associated with increased error rates as well as larger N400 components known to index semantic/conceptual processing cost. These findings thus suggest that the words automatically activated visuospatial simulations of their referents and that semantic/conceptual processing difficulty arose when the vertical arrangement of the word pairs was inconsistent with those simulations. In line with this interpretation, these effects were not present in Experiment 2 when the words of each pair were presented in succession in the middle of the screen. Overall, these results provide evidence that perceptual simulations contribute to some of the underlying processes of the N400 component (see video abstract, Supplemental digital content 1, http://links.lww.com/WNR/A304).

Cerebral asymmetry in the control of cardiovascular functioning: evidence from lateral vibrotactile stimulation.

Research has supported hemispheric specialisation in the regulation of cardiovascular functioning, with the left hemisphere being associated with parasympathetic functioning and the right hemisphere with sympathetic functioning. We sought to investigate this relationship further using vibrotactile stimulation applied to the palms. Our prediction was that vibrotactile stimulation applied to the left hand would result in increased heart rate and blood pressure, and that stimulation applied to the right hand would result in decreased heart rate and blood pressure. The results indicated significant differences in heart rate change scores in the predicted direction. No differences were noted for systolic or diastolic blood pressure. Hence the findings provide partial support for the lateralisation of autonomic functions.