Rhythmic temporal structure at encoding enhances recognition memory

Presenting events in a rhythm has been shown to enhance perception and facilitate responses for stimuli that appear in synchrony with the rhythm, but little is known about how rhythm during encoding influences later recognition. In this study, participants were presented with images of everyday objects in an encoding phase prior to a recognition task in which they judged whether or not objects were previously presented. Blockwise, object presentation during encoding followed either a rhythmic (constant, predictable) or arrhythmic (random, unpredictable) temporal structure, of which participants were unaware. Recognition was greater for items presented in a rhythmic relative to an arrhythmic manner. During encoding, there was a Dm effect with larger positivity for rhythmic over arrhythmic stimuli. At recognition, memory specific ERP components were differentially affected by temporal structure: the FN400 old/new effect was unaffected by rhythmic structure, whilst the late positive component (LPC) old/new effect was observed only for rhythmically encoded items. Taken together, this study provides new evidence that memory specific processing at recognition is affected by temporal structure at encoding

Rhythmic temporal structure at encoding enhances recognition memory

Presenting events in a rhythm has been shown to enhance perception and facilitate responses for stimuli that appear in synchrony with the rhythm, but little is known about how rhythm during encoding influences later recognition. In this study, participants were presented with images of everyday objects in an encoding phase prior to a recognition task in which they judged whether or not objects were previously presented. Blockwise, object presentation during encoding followed either a rhythmic (constant, predictable) or arrhythmic (random, unpredictable) temporal structure, of which participants were unaware. Recognition was greater for items presented in a rhythmic relative to an arrhythmic manner. During encoding, there was a Dm effect with larger positivity for rhythmic over arrhythmic stimuli. At recognition, memory specific ERP components were differentially affected by temporal structure: the FN400 old/new effect was unaffected by rhythmic structure, whilst the late positive component (LPC) old/new effect was observed only for rhythmically encoded items. Taken together, this study provides new evidence that memory specific processing at recognition is affected by temporal structure at encoding

Bridging neuroscience and robotics: spiking neural networks in action

Robots are becoming increasingly sophisticated in the execution of complex tasks. However, an area that requires development is the ability to act in dynamically changing environments. To advance this, developments have turned towards understanding the human brain and applying this to improve robotics. The present study used electroencephalogram (EEG) data recorded from 54 human participants whilst they performed a two-choice task. A build-up of motor activity starting around 400 ms before response onset, also known as the lateralized readiness potential (LRP), was observed. This indicates that actions are not simply binary processes but rather, response-preparation is gradual and occurs in a temporal window that can interact with the environment. In parallel, a robot arm executing a pick-and-place task was developed. The understanding from the EEG data and the robot arm were integrated into the final system, which included cell assemblies (CAs)—a simulated spiking neural network—to inform the robot to place the object left or right. Results showed that the neural data from the robot simulation were largely consistent with the human data. This neurorobotics study provides an example of how to integrate human brain recordings with simulated neural networks in order to drive a robot

Temporal expectation improves recognition memory for spatially attended objects

Recent evidence suggests that temporal expectation is beneficial to memory formation. Rhythmic presentation of stimuli during encoding enhances subsequent recognition and is associated with distinct neural activity compared with when stimuli are presented in an arrhythmic manner. However, no prior study has examined how temporal expectation interacts with another important form of facilitation – spatial attention – to affect memory. This study systematically manipulated temporal expectation and spatial attention during encoding to examine their combined effect on behavioural recognition and associated ERPs. Participants performed eight experimental blocks consisting of an encoding phase and recognition test, with EEG recorded throughout. During encoding, pairs of objects and checkerboards were presented and participants were cued to attend to the left or right stream and detect targets as quickly as possible. In four blocks stimulus presentation followed a rhythmic (constant, predictable) temporal structure, and in the other four blocks stimulus onset was arrhythmic (random, unpredictable). An interaction between temporal expectation and spatial attention emerged, with greater recognition in the rhythmic than the arrhythmic condition for spatially attended items. Analysis of memory specific ERP components uncovered effects of spatial attention. There were late positive component (LPC) and FN400 old/new effects in the attended condition for both rhythmic and arrhythmic items, while in the unattended condition there was an FN400 old/new effect, and no LPC effect. The study provides new evidence that memory improvement as a function of temporal expectation is dependent upon spatial attention

Orienting of willed temporal attention: an EEG study

Temporal attention enables people to select relevant stimuli across time allowing for prioritisation of information. In most studies on temporal orienting external cues have been used to direct participants' attention. However, in everyday life, we also make internal choices, without external cues, of when to orient our attention. Recent studies in visual-spatial attention developed a paradigm aiming to explore how voluntary attention is initiated and controlled when no direct instructions are used. This paradigm includes a new type of trial in which a participant is asked to choose where to orient their attention (willed attention) in contrast to being instructed where to orient their attention (instructed attention). The current study draws on this distinction and it aims to explore whether and how willed temporal attention affects behaviour and whether it is different from instructed temporal attention by looking at both behavioural data as well as EEG. To explore that question the temporal cueing task was used in which a cue instructed a participant to anticipate either short (800 ms) or a long (2000 ms) interval between cue and target presentation times. Alternatively, a cue instructed a participant to decide for themselves to expect the target after one of these two intervals. The experiment demonstrated no significant differences in RTs and EEG recordings. However, a difference between two attention types in the CNV recorded in the time interval directly preceding the target in the short cue-target interval showed a medium effect size. Furthermore, a comparison of the CNV recorded in the willed and instructed attention in the post cue time interval demonstrated medium effect size with posterior scalp distribution. It was only recorded in the short cue-target interval. There, also, was a lateralised activity in the N1 time range in the instructed attention condition. Finally, a small decrease in the power of the theta activity was observed in the willed attention condition in the long cue-target interval at the Fz electrode. These differences could potentially become significant with more power. To the author's knowledge, this is the first study on electrophysiological correlates of willed temporal attention, and it demonstrates the feasibility of the paradigm used

The effect of aging and rhythmic temporal structure during encoding on recognition memory: an EEG Study

Aging deficits in memory have long been established in the literature, however, little has been done to investigate how environmental factors can be used to ameliorate age related declines in memory functioning. Recent research in recognition memory suggests that increased temporal expectancy during encoding can benefit recognition memory at retrieval in a younger adult sample. The current study aimed to investigate whether the benefit to recognition memory, and associated neural processes, observed in young adults is also evident in normal aging. Unfortunately, due to national restrictions affecting data collection, no older participants were able to be tested. As such, the current project resolved to provide a proof of concept to inform an investigation of the originally intended scope. Ten young participants (M age = 23.5; SD = 2.22) were exposed to pictures of everyday objects in 3 rhythmic and 3 arrhythmic encoding blocks, after which they performed a recognition memory test containing previously studied and new objects. A clear trend suggesting better memory following rhythmic encoding was observed, but no significant difference between conditions emerged. Furthermore, analysis of relevant ERP components uncovered no old/new effect in relation to the LPC or the LFE. Conversely, the FN400 displayed an old/new effect. Thus, the temporal manipulation did not result in significant differences in recognition, but it should be noted that the study is underpowered. However, participants did display a good ability to discriminate stimuli, and in addition RT differences between correct and incorrect recognition judgements and an FN400 old/new effect suggest that the paradigm is effective and sensitive to processing differences between conditions. Recognition could be detected by the FN400 in the present experiment. However, trends in recognition ability between temporal structures suggest that an insufficient sample size is likely to have caused the lacking significant temporal effects. As such, the paradigm is appropriate for extension including a larger sample size and the planned comparison of age groups