Spreading activation in nonverbal memory networks.

Theories of spreading activation primarily involve semantic memory networks. However, the existence of separate verbal and visuospatial memory networks suggests that spreading activation may also occur in visuospatial memory networks. The purpose of the present investigation was to explore this possibility. Specifically, this study sought to create and describe the design frequency corpus and to determine whether this measure of visuospatial spreading activation was related to right hemisphere functioning and spreading activation in verbal memory networks. We used word frequencies taken from the Controlled Oral Word Association Test and design frequencies taken from the Ruff Figural Fluency Test as measures of verbal and visuospatial spreading activation, respectively. Average word and design frequencies were then correlated with measures of left and right cerebral functioning. The results indicated that a significant relationship exists between performance on a test of right posterior functioning (Block Design) and design frequency. A significant negative relationship also exists between spreading activation in semantic memory networks and design frequency. Based on our findings, the hypotheses were supported. Further research will need to be conducted to examine whether spreading activation exists in visuospatial memory networks as well as the parameters that might modulate this spreading activation, such as the influence of neurotransmitters.

Administration of exogenous melatonin increases spreading activation in lexical memory networks.

OBJECTIVE: Several studies have examined the effect of exogenous melatonin on memory and cognitive functioning. Many of these investigations have reported improvement in recall and recognition as well as performance on various other indices of neuropsychological functioning. However, there have been no investigations reported that have examined the effects of exogenous melatonin administration on spreading activation in lexical and semantic memory networks. Hence, the purpose of this investigation was to determine the effects of melatonin on spreading activation. METHODS: Participants were randomly assigned to either a 3-mg or 5-mg dose group, and spreading activation was measured both before and after administration. Spreading activation was measured by calculating the average word frequencies for words generated on the controlled oral word association test and the semantic fluency test. RESULTS: A significant main effect for time was found, with the controlled oral word association test average word frequency being significantly higher at baseline than after taking melatonin. Also, a significant group × time interaction was found when using log transformed data. Multiple comparisons indicated that the 3-mg group exhibited significantly greater spreading activation following melatonin than the 5-mg group. The results indicate that melatonin may produce an increase in spreading activation in lexical memory networks. These results potentially provide an explanation for the benefits of melatonin on memory functioning.

Recall of word lists is enhanced with increased spreading activation.

Some evidence exists supporting a relationship between spreading activation in semantic/lexical memory networks and episodic memory. However, the results have been mixed and there have been no investigations examining whether a relationship exists between variability in spreading activation and episodic memory. Hence, we sought to investigate these potential relationships. Thirteen individuals were administered the Hopkins Verbal Learning Test-Revised (HVLT-R) and the Controlled Oral Word Association Test (COWAT). The average word frequency of all the "F" words generated on the COWAT was used as a measure of spreading activation. Variability in spreading activation was assessed by calculating the variability of the word frequencies from the COWAT across time. The results confirmed our hypotheses, with significant negative correlations found between free recall on the HVLT-R and both the average word frequency and measures of variability in spreading activation.

Acetylcholinesterase inhibitors reduce spreading activation in dementia.

Alzheimer's disease is associated with degeneration of the cholinergic system, which affects memory and attention functioning. Acetylcholinesterase inhibitors (AChEI) have been found to increase attention and given this effect might reduce spreading activation of memory nodes in lexical/semantic networks. We sought to determine whether this effect of AChEIs existed in a group of patients with dementia. A mixed sample of 34 patients with dementia (17 taking AChEIs and 17 not taking these medications) were administered the Controlled Oral Word Association Test and the Animal Naming Test. The average word frequency for their responses was obtained and used as a measure of spreading activation. Patients taking AChEIs had a significantly higher average word frequency for the COWAT as compared to those not taking AChEIs. No difference was found for the average word frequencies for the AN test. Administration of AChEIs appears to reduce spreading activation, possibly due to cholinergic innervations of the frontal cortex.

Increased spreading activation in depression.

The dopaminergic system is implicated in depressive disorders and research has also shown that dopamine constricts lexical/semantic networks by reducing spreading activation. Hence, depression, which is linked to reductions of dopamine, may be associated with increased spreading activation. However, research has generally found no effects of depression on spreading activation, using semantic priming paradigms. We used a different paradigm to investigate the relationship between depression and spreading activation, one based on word frequencies. Our sample included 97 undergraduates who completed the BDI-II and the Controlled Oral Word Association test as well as the Animal Naming test. The results indicated that the group scoring within the depressed ranged evidenced greater spreading activation as compared to those who scored within the normal range on the BDI-II. The implications of these results as they relate to creativity in depression is discussed.