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Contains fulltext : 241277.pdf (Publisher’s version ) (Open Access) According to dual-process signal-detection (DPSD) theories, short- and long-term recognition memory draws upon both familiarity and recollection. It remains unclear how primate prefrontal cortex (PFC) contributes to these processes, but frequency-specific neuronal activities are considered to play a key role. In Experiment 1, nonhuman primate (NHP) local field potential (LFP) electrophysiological recordings in macaque left dorsolateral PFC (dlPFC) revealed performance-related differences in a low-beta frequency range during the sample presentation phase of a visual object recognition memory task. Experiment 2 employed a similar task in humans and targeted left dlPFC (and vertex as a control) with repetitive transcranial magnetic stimulation (rTMS) at 12.5 Hz during occasional sample presentations. This low-beta frequency rTMS to dlPFC decreased DPSD derived indices of recollection, but not familiarity, in subsequent memory tests of the targeted samples after short delays. The same number of rTMS pulses over the same total duration albeit at a random frequency had no effect on either recollection or familiarity. Neither stimulation protocols had any causal effect upon behaviour when targeted to the control site (vertex). In this study, our hypotheses for our human TMS study were derived from our observations in NHPs; this approach might inspire further translational research through investigation of homologous brain regions and tasks across species using similar neuroscientific methodologies to advance the neural mechanism of recognition memory in primates. 28 p.

According to dual-process theories, recognition memory draws upon both familiarity and recollection. It remains unclear how primate prefrontal cortex (PFC) contributes to familiarity and recollection processes but frequency-specific neuronal activities are considered to play a key role. Here, non-human primate (NHP) electrophysiological local field potential (LFP) recordings first showed that a specific subregion of macaque PFC (i.e., dorsolateral PFC, dlPFC) was implicated in task performance at a specific frequency (i.e., increased beta power in the 10-15 Hz range observed in correct versus error trials) in a specific phase of a recognition memory task (i.e., during sample presentation). Then, to assess generalization to humans and causality we targeted left human dlPFC (BA 9/46) as well as left dorsomedial prefrontal cortex (BA 8/9) for comparison, and also vertex as a control, with transcranial magnetic stimulation at a frequency in the middle of the low-beta range observed in NHP (i.e. 12.5 Hz) and compared that to non-frequency-specific stimulation, and also to a no-stimulation control, during occasional sample presentations within a similar task. Hence we investigated hypotheses about the causal importance for human memory of a location-specific, frequency-specific, and task-epoch-specific intervention derived directly from the NHP electrophysiological observations. Using a dual-process signal detection (DPSD) model based on analysing receiver operating characteristics (ROC) curves, we showed beta-frequency TMS caused decreased recollection when targeted to human dlPFC, but enhanced familiarity when targeted to dorsomedial prefrontal cortex. Non-frequency-specific patterns of stimulation to all sites, and beta-frequency stimulation to vertex, were all without behavioural effect. This study provides causal evidence that PFC-mediated contributions to object recognition memory are modulated by beta-frequency activity; more broadly it provides translational evidence bridging NHPs and humans by emphasizing functional roles of beta-frequency activity in homologous brain regions in recognition memory.Highlightslow beta power in NHP dlPFC during stimulus encoding was related to behaviourhuman rTMS study used parameters derived from NHP observations to test causalitylow beta rTMS to human dlPFC, but not dmPFC, impairs recollectionlow beta rTMS to human dmPFC, but not dlPFC, enhances familiarityprovides cross-species validation of prefrontal beta power to primate recognition

We investigated whether there are reliable crossmodal associations between foods/flavours and words in neurologically normal individuals. Participants were given a range of foods to taste, and had to rate each one along a number of dimensions. These included scales anchored with the words "takete/maluma" and "bouba/kiki". The results highlight the existence of robust crossmodal associations between complex foods/flavours and words in normal (i.e., nonsynesthetic) individuals. For example, crisps (potato chips) and cranberry sauce are rated as being more "takete" than brie cheese, while mint chocolate is rated as more "kiki" than regular chocolate. On the basis of these results, we suggest that our brains can extract supramodal/conceptual properties from foods/flavours (just as has been demonstrated previously using auditory and visual stimuli) and meaningfully match them crossmodally. The possibility that this process is based on the global Gestalt of a food rather than on any specific sensory qualities is also discussed. © 2010 Psychology Press.

A substantial body of literature has proposed a role for dorsolateral prefrontal cortex (dlPFC) in supporting behavioural adaptation during conflict tasks. The vast majority of the evidence in support of this interpretation comes from neuroimaging studies. However, in order to unequivocally ascribe such a role to dlPFC, it is important to determine whether or not it is essential for this mechanism, and this can only be achieved by lesioning the area or interfering with its activity. In this study, we investigated the effects of repeated Transcranial Magnetic Stimulation (rTMS) to dlPFC on performance on a conflict version of a Wisconsin Card Sorting Test analogue (used previously in circumscribed lesion studies in monkeys) in neurologically healthy human participants. Our results supported the view of dlPFC as a fundamental structure for optimal conflict-induced behavioural adaptation, as stimulation cancelled out the adaptation effect normally observed on control trials. We show that there is some indication of differential modulation of trial types by stimulation and we hypothesize that this might suggest a role for dlPFC in conflict-induced adaptation that is more specifically concerned with the maintenance of conflict-history information online across trials., Highlights • Dorsolateral prefrontal cortex stimulation abolishes conflict-induced adaptation. • Adaptation is abolished via differential modulation of trial types. • Dorsolateral prefrontal areas may aid adaptation via conflict history maintenance.