Using temporo-spatial principal component analysis as tool to dissociate latent ERP components of episodic memory retrieval: Objectifying time-window selection for overlapping ERP components.

This report details how principal component analysis (PCA) can be used as a valuable tool to dissociate latent ERP components, even when considerable temporal and spatial overlap makes it difficult to discern ERP effects in standard time windows. We illustrate our methodological approach in a data set from a recognition memory paradigm, in which event-related potential (ERP) correlates of familiarity, recollection and the late parietal negativity (LPN) were partially overlapping. By adapting standard time windows based on the results of a temporo-spatial PCA, small yet reliable ERP correlates reflecting familiarity and recollection for identical items and late recollection for changed items were identified, complementing the result pattern observed in behavioral performance. Due to similar temporo-spatial characteristics and opposing polarities in late parietal ERP correlates associated with memory retrieval, component overlap is often observed in this field of research. Hence, the complex interplay of several processes underlying higher cognitive functions such as memory retrieval may interfere with standard ERP assessment. In such instances, PCA can provide promising ways to objectively assess time window selection for subsequent ERP analyses.

Neural correlates of feedback processing during a sensory uncertain speech - nonspeech discrimination task.

Performance feedback during a speech-nonspeech discrimination task was used to investigate (neuro-)cognitive processes underlying feedback processing under uncertainty. Sensory uncertainty was manipulated by creating stimuli that were stepwise morphs of the German vowels /a/ and /a:/ (speech) and their spectrally rotated counterparts (non-speech). The anterior N1 associated with early attentional modulation was largest following negative feedback. Both negative and uninformative feedback showed larger FRN amplitudes, suggesting a classification as worse than expected. Sensory uncertainty affected only the feedback-P3, in terms of larger amplitudes for (1) stimuli with high uncertainty and (2) positive feedback. Confidence ratings revealed that sensory uncertainty reduced the accuracy of stimulus categorization, but did not modulate participants' response confidence. Results suggest that feedback processing follows three distinct and successive stages, starting with initial screening for behavioral relevance (anterior N1, enhanced for unexpected negative feedback), followed by a binary valence distinction (FRN), and a more detailed analysis (P3).

Neuronal oscillations reveal the processes underlying intentional compared to incidental learning in children and young adults.

This EEG study investigated the neuronal processes during intentional compared to incidental learning in young adults and two groups of children aged 10 and 7 years. Theta (3-8 Hz) and alpha (10-16 Hz) neuronal oscillations were analyzed to compare encoding processes during an intentional and an incidental encoding task. In all three age groups, both encoding conditions were associated with an increase in event-related theta activity. Encoding-related alpha suppression increased with age. Memory performance was higher in the intentional compared to the incidental task in all age groups. Furthermore, intentional learning was associated with an improved encoding of perceptual features, which were relevant for the retrieval phase. Theta activity increased from incidental to intentional encoding. Specifically, frontal theta increased in all age groups, while parietal theta increased only in adults and older children. In younger children, parietal theta was similarly high in both encoding phases. While alpha suppression may reflect semantic processes during encoding, increased theta activity during intentional encoding may indicate perceptual binding processes, in accordance with the demands of the encoding task. Higher encoding-related alpha suppression in the older age groups, together with age differences in parietal theta activity during incidental learning in young children, is in line with recent theoretical accounts, emphasizing the role of perceptual processes in mnemonic processing in young children, whereas semantic encoding processes continue to mature throughout middle childhood.

Sometimes we have to intentionally focus on the details: Incidental encoding and perceptual change decrease recognition memory performance and the ERP correlate of recollection.

Prior studies suggest that memory retrieval is based on two independent processes: Recollection and familiarity. Here, we investigated the role of incidental and intentional encoding, and specifically whether perceptual changes between study and test affects behavioral and electrophysiological correlates of both retrieval processes. During retrieval, participants distinguished between identical and changed exemplars as well as novel distractors. Following incidental encoding, participants had difficulty identifying changed exemplars; item and feature recognition increased after intentional encoding, in particular for changed exemplars. Reflecting this increase in memory performance, the ERP correlate of recollection was larger after intentional encoding and for identical item repetitions, whereas the ERP correlate for familiarity was largely unaffected. Pre-response old/new effects corresponding to later aspects of recollection (700-1000 ms relative to stimulus onset) were larger in response-compared to stimulus-locked averages, but also of similar magnitude for identical and changed exemplars. These results corroborate previous findings suggesting that the electrophysiological signature of recollection is modulated as a function of memory performance. The role of task characteristics and material retrieved from memory for modulations in familiarity-based retrieval processes is discussed.

Evaluating the effectiveness of a memory aid system.

BACKGROUND: The ability to remember future intentions is compromised in both healthy and cognitively impaired older adults. Assistive technology provides older adults with promising solutions to cope with this age-related problem. However, the effectiveness and efficiency of such systems as memory aids is seldom evaluated in controlled, randomized trials. OBJECTIVES: We evaluated the effectiveness of a memory aid system, the InBad (engl. InBath), for bathroom-related daily care. Conceptually, the InBad learns user behavior patterns and detects deviations from the learned pattern in order to notify the user of a forgotten task. METHODS: We simulated a challenging morning routine consisting of 22 bathroom activities with a sample of 60 healthy older adults. Participants were randomly assigned to three groups: (1) 'no memory support', i.e., participants received no support at all, (2) 'list support', i.e., participants could retrieve a list of all activities, and (3) 'system support', i.e., participants received prompts for specific activities that had not yet been executed. RESULTS: Both support groups executed significantly more activities compared to the 'no support' group. In addition, system support resulted in significantly better performance compared to list support with no significant differences between the two groups in overall task duration. CONCLUSION: The assistive support system was the most effective and efficient memory aid. The results suggest that assistive technology has the potential to enable older adults to remain safe and independent in their own home.