Manuel Sebastián

Ageing affects event-related potentials and brain oscillations: a behavioral and electrophysiological study using a haptic recognition memory task.

In this electrophysiological study, we investigated the effects of ageing on recognition memory for three-dimensional (3D) familiar objects presented to touch in a continuous paradigm. To examine changes in event-related potentials (ERPs) and brain oscillations, we recorded the EEGs of healthy groups of young (n=14; mean age=32.3 years) and older adults (n=14; mean age=65.1). Both age groups exhibited similar accuracy and exploration times when making old-new judgments. Young and older participants showed a marginally significant ERP old/new effect widely distributed over the scalp between 550-750 ms. In addition, the elders showed lower amplitude than younger participants within 1200-1500 ms. There were age-related differences in brain oscillations as measured by event-related spectral perturbation (ERSP). Older adults showed greater alpha and beta power reductions than young participants, suggesting the recruitment of additional neural resources. In contrast, the two age groups showed a reliable old/new effect in the theta band that temporarily overlapped the ERP old/new effect. The present results suggest that despite similar behavioral performance, the young and older adults recruited different neural resources to perform a haptic recognition task.

Effects of normal aging on event-related potentials and oscillatory brain activity during a haptic repetition priming task.

This study reports neural repetition effects in young and older adults while performing a haptic repetition priming task consisting in the detection of the bilateral symmetry of familiar objects. To examine changes in event-related potentials (ERPs) and induced brain oscillations of object repetition priming with aging, we recorded EEGs of healthy groups of young (n=14; mean age=29.93 years) and older adults (n=15; mean age=66.4). Both groups exhibited similar behavioral haptic priming across repetitions, although young adults responded faster than the older group. Young and older adults showed ERP repetition enhancement at the 500-900 ms time window. In contrast, only the young participants showed ERP repetition suppression at the 1200-1500 ms segment. The results from the induced oscillations showed more positive amplitudes in young than in older adults at theta, alpha and beta frequencies (4-30 Hz). In addition, we found amplitude modulation related to stimulus repetition in the upper alpha and low beta sub-bands only in young adults (1250-1750 ms).The results suggest that although behavioral priming is spared with age, normal aging affects ERPs and oscillatory responses when performing an incidental priming symmetry detection task with haptically explored objects.

A close look into the near/far space division: a real-distance ERP study.

For the first time this study measures the electric brain activation in a semi-real scenario to investigate the representation of objects in the near/far space. We recorded electrical brain activity from a group of 22 participants who had to indicate whether or not they could reach or not several objects that appeared along a 52″ touchscreen display. We replicated previous results showing that reaction time to objects located in the near space was significantly faster than to objects located in far space. The effects of object location found here were significant even when their hand was not visible to them and retracted from the objects. ERP analysis showed a consistent N1 visual component with faster latencies and greater amplitudes for objects in near space. Importantly, this latency difference was not linked only to the physical distance but to a psychological division between near and far space based on their interactive potential (e.g. reachable vs. not reachable). At later stages LPP results showed significant effects of arousal at occipital electrode sites while parietal scalp locations were sensitive to spatial location supporting a ventral/dorsal dissociation of neuropsychological space.

Effects of negative content on the processing of gender information: An event-related potential study

Previous research on emotion in language has mainly concerned the impact of emotional information on several aspects of lexico-semantic analyses of single words. However, affective influences on morphosyntactic processing are less understood. In the present study, we focused on the impact of negative valence in the processing of gender agreement relations. Event-related potentials (ERPs) were recorded while participants read three-word phrases and performed a syntactic judgment task. Negative and neutral adjectives could agree or disagree in gender with the preceding noun. At an electrophysiological level, the amplitude of a left anterior negativity (LAN) to gender agreement mismatches decreased in negative words, relative to neutral words. The behavioral data suggested that LAN amplitudes might be indexing the processing costs associated with the detection of gender agreement errors, since the detection of gender mismatches resulted in faster and more accurate responses than did the detection of correct gender agreement relations. According to this view, it seems that negative content facilitated the processes implicated in the early detection of gender agreement mismatches. However, gender agreement violations in negative words triggered processes involved in the reanalysis and repair of the syntactic structure, as reflected in larger P600 amplitudes to incorrect than to correct phrases, irrespective of their emotional valence.

A new device to present textured stimuli to touch with simultaneous EEG recording

The study of touch has recently grown, due mainly to the extensive use of several types of actuators that stimulate several subsystems of touch. There is a widespread interest in applying these mechanisms to the study of the neurophysiological correlates of tactual perception. In this article, we present a new device (the tactile spinning wheel [TSW]) for delivering textured surfaces to the finger pad. The TSW allows one to control several parameters of the stimulation (angular speed, texture, etc.) and, connected to an EEG recording system, makes it possible to study neural electrophysiological events. The device consists of a rotating platform on which the tactile stimuli are fixed, a system that synchronizes stimuli onset with the EEG system, and an electronic interface that controls the platform. We present the technical details of the TSW, its calibration, and some experimental results we have obtained with this device.

ERP evidence of tactile texture processing: Effects of roughness and movement

Psychological and neurophysiological studies have investigated the peripheral neural mechanisms implicated in tactile roughness perception. However, the cortical mechanisms involved in roughness processing are not well understood. In the present study, we used behavioural data and event-related evoked potentials (ERPs) to investigate the extent to which two tactile stimuli varying in roughness (triangular gratings peak-to-peak spacing of 1.6 mm and 2.8 mm) and movement (the time available for tactile contact with the surface) modulate early stages of brain activation. Behavioral results showed that participants discriminate the two levels of roughness at the three velocities explored in the study but they were judged as equivalent in pleasantness. The ERP results showed a biphasic early-fast N1-P2 deflection. The N1 and P2 peaks to the smoother texture occur earlier than that of the rougher texture. Considering velocity, the N1 onset occurs later for the slowest velocity, followed by the intermediate velocity and earlier for the fastest velocity and the three velocities differ significantly. LORETA analysis showed that N1 and P2 components of surface roughness are both related to the activation produced in the somatosensory cortex and posterior cingulated respectively, suggesting that these areas might be involved in the sensory processing of roughness.

Working Memory for Visual and Haptic Targets: A Study Using the Interference Paradigm

We investigated the effect of different types of interference in visual and haptic working memory using a dual-task paradigm. At encoding, 16 young adults performed both, a haptic and a visual primary task followed by the performance of a secondary interference task during a retention interval. The interference task could be a haptic (spatial), visual (spatial), auditory, or control (visual-static) task. The idea was to study the influence of spatial and verbal interference on working memory for spatial targets encoded visually or haptically. The results indicated that the auditory interference task did not deteriorate performance compared to the control condition in which participants performed the visual-static task. The negative effects of spatial interference increased when both the primary and secondary tasks were performed using the same modality. Spatial interference selectively deteriorated both visual and haptic working memory but more strongly the later.

Modulations in low-frequency EEG oscillations in the processing of tactile surfaces

The present study investigated low-oscillatory (theta band, 3-7 Hz) modulations induced by tactile roughness stimulations under two attention-demanding conditions. Four levels of roughness were presented under low-demanding and high-demanding conditions. In both conditions, an oddball paradigm was used to present three target surfaces varying in roughness (low, mid, and high levels of roughness), and a nontarget flat surface. The results showed that centro-parietal theta oscillations are involved in allocating attentional resources when participants have to update new information induced by incoming haptic stimuli. Theta power was higher in the high-demanding task compared to the low-demanding. Furthermore, theta power varied depending on tactile roughness but not in a linear manner. This was interpreted as that theta oscillations were sensitive not only to task difficulty but also to physical properties.

Haptic recognition memory following short-term visual deprivation: Behavioral and neural correlates from ERPs and alpha band oscillations

In the current study, we investigated the effects of short-term visual deprivation (2 h) on a haptic recognition memory task with familiar objects. Behavioral data, as well as event-related potentials (ERPs) and induced event-related oscillations (EROs) were analyzed. At the behavioral level, deprived participants showed speeded reaction times to new stimuli. Analyses of ERPs indicated that starting from 1000 ms the recognition of old objects elicited enhanced positive amplitudes only for the visually deprived group. Visual deprivation also influenced EROs. In this sense, we observed reduced power in the lower-1 alpha band for the processing of new compared to old stimuli between 500 and 750 ms. Overall, our data showed improved haptic recognition memory after a short period of visual deprivation. These effects were thought to reflect a compensatory mechanism that might have developed as an adaptive strategy for dealing with the environment when visual information is not available.