Beyond visual imagery: How modality-specific is enhanced mental imagery in synesthesia?

Synesthesia based in visual modalities has been associated with reports of vivid visual imagery. We extend this finding to consider whether other forms of synesthesia are also associated with enhanced imagery, and whether this enhancement reflects the modality of synesthesia. We used self-report imagery measures across multiple sensory modalities, comparing synesthetes’ responses (with a variety of forms of synesthesia) to those of non-synesthete matched controls. Synesthetes reported higher levels of visual, auditory, gustatory, olfactory and tactile imagery and a greater level of imagery use. Furthermore, their reported enhanced imagery is restricted to the modalities involved in the individual’s synesthesia. There was also a relationship between the number of forms of synesthesia an individual has, and the reported vividness of their imagery, highlighting the need for future research to consider the impact of multiple forms of synesthesia. We also recommend the use of behavioral measures to validate these self-report findings.     

Perceptual processing affects the reactivation of a sensory dimension during a categorization task

According to grounded theories of cognition, knowledge is grounded in its sensory-motor features. Therefore, perceptual and conceptual processing should be based on the same distributed system so that conceptual and perceptual processes should interact. The present study assesses whether gustatory stimulation (participants tasted a sweet or a nonsweet yoghurt) could influence performance on a categorization task that involves the reactivation of the same sensory dimension. The results indicate that participants were slower (Experiment 1) or faster (Experiment 2), respectively, at categorizing pictures as representing edible sweet stimuli when they either simultaneously or had previously tasted a sweet yoghurt as compared to a nonsweet yoghurt. These results confirm the significant overlap between perceptual and memory mechanisms and suggest the functional equivalence between perceptually present and perceptually absent (memory reactivated) dimensions.     

Immediate recognition memory for wine

We describe a preliminary investigation concerning the short-term recognition memory function for gustatory stimuli (wines). In Experiment 1A, 24 non-expert wine drinkers completed a yes/no recognition task for 3-wine sequences. For the raw recognition scores, the serial position function comprised both primacy and recency. Recency did not, however, achieve significance for the d′ scores. In Experiment 1B, 24 participants completed the same yes/no recognition task for 3-visual matrix sequences. In contrast to Experiment 1A, the serial position function comprised recency and an absence of primacy. We argue that the presence of primacy for the wine sequences cannot be interpreted via a verbal labelling strategy, nor can it be interpreted via proactive interference from the first wine in the list on subsequent list items. The result suggests qualitative differences in the memory processing for gustatory and non-verbal visual stimuli.     

Role of cholinergic system on the construction of memories: taste memory encoding

There is a large body of evidence suggesting that cholinergic activity is involved in memory processes. It seems that cholinergic activity is essential to learn several tasks and recent works suggest that acetylcholine plays an important role during the early stages of memory formation. In this review, we will discuss the results related to taste memory formation, focusing particularly on the conditioned taste aversion paradigm. We will first give evidence that nucleus basalis magnocellularis is involved in taste memory formation, due to its cholinergic projections. We then show that the cholinergic activity of the insular (gustatory) cortex is related to the taste novelty, and that the cholinergic signals initiated by novelty are crucial for taste memory formation. Then we present recent data indicating that cortical activation of muscarinic receptors is necessary for taste trace encoding, and also for its consolidation under certain circumstances. Finally, interactions between the cholinergic and other neuromodulatory systems inducing intracellular mechanisms related to plastic changes will be proposed as important processes underlying gustatory memory trace storage.