Jon and Alex are both attending the 2019 Cognitive Neuroscience Society Annual meeting in San Francisco. Both are presenting posters.
Jon’s poster presentation:
The poster is being presented in session F in location F13 on Tuesday, March 26, 8:00-10:00 am, Pacific Concourse.
Successful classification of attentional tasks by power modulations in the alpha frequency bandwidth
Jonathan Silas1, Irene Varela Leniz2, Eris Chinellato1, Bettina Forster3 and Alexander Jones1
1Middlesex University London, UK,
2Mondragon Unibertsitatea, Mondragón, Spain,
3City University London, London, UK
Power modulations at the alpha frequency recorded over the somatosensory cortex have been shown to systematically vary depending upon attention to tactile stimuli. When attention is orientated endogenously to the left or right, alpha power has been shown to be heavily lateralised in the brain. However, when attention is cued exogenously, somatosensory alpha lateralisation decreases. We sought to ask whether alpha power measured at electrodes over the somatosensory cortex contained sufficient information to categorise the attentional processes engaged in by the participant. Participants completed three attentional tasks whilst we recorded their electroencephalography (EEG). Each task included a lateralised cue to the left or right index finger followed by a target (after 1000 ms) to the same or opposite hand. In the exogenous task, the cue provided no information about the location of the upcoming target. In the endogenous predictive task, the cue was predictive of the target to the same hand (80%) and in a counter-predictive task, to the opposite hand. Using a machine classifier (random forest) trained on 90% of the data during the cue-target interval we show that central alpha power is sufficient to categorise the tasks above chance in the remaining 10% of data. Further, we find that categorisation is best in the 300-400ms time window and that the contribution by the hemisphere contralateral to the stimuli is better early in the cue-target interval, whilst ipsilateral hemispheric contribution is best late, just before target onset. These findings suggest a necessary role of alpha power in attentional mechanisms.
Alex’s poster presentation:
The poster is being presented in session F in location F88 on Tuesday, March 26, 8:00-10:00 am, Pacific Concourse.
Rhythmic encoding improves recognition memory
Alexander Jones* and Emma Ward*
*Middlesex University London
There has recently been an increased interest in the way temporal expectancies shape perception and drive behaviour. Research has observed that intrinsic neural oscillations can entrain to external rhythms by aligning the firing pattern of neurons. This entrainment has shown to enhance perception and facilitate behaviour for stimuli that appear in phase with the rhythm, yet little is known about how temporal expectation during encoding influences subsequent memory. Participants in the present study were presented with a rapid succession of everyday objects in an encoding phase and asked in a subsequent recognition test phase to judge whether individually presented objects were presented before (old) or not (new). Importantly, the presentation of objects in the encoding phase followed a either rhythmic or arrhythmic temporal pattern, of which participants were not made aware. Recognition was significantly greater for items that were presented rhythmically compared to those presented arrhythmically. There was evidence entrainment with increased phase locking for rhythmic over arrhythmic stimuli during encoding. Moreover, memory specific ERP components at test phase were influenced by rhythmic encoding. Specifically, the FN400 old/new effect was present in both conditions, but a late positive component (LPC) old/new effect was only observed for rhythmically encoded items. This parietal old/new effect (LPC) has been proposed as an index of recollection, specifically linked to memory for the contextual details associated with the encounter with the item. The study provides new evidence through EEG and behavioural measures that presenting stimuli in a rhythmic manner provides a benefit to recognition memory.