Stefania Righi

Anxiety, cognitive self-evaluation and performance: ERP correlates

The relation between anxiety, cognitive self-evaluation, performance, and electrical brain activity (event-related potentials, ERPs) in a sustained attention task (Go/NoGo; SART) was investigated in 18 participants. No significant correlation was found between reaction times and anxiety (assessed by State and Trait Anxiety Inventory or STAI), and cognitive self-evaluation (assessed by Cognitive Failures Questionnaire or CFQ). N2 (ERP time-window 250-350ms) and P3 (350-650ms) amplitudes were found to be related to anxiety and cognitive self-evaluation. N2 amplitude increased in trait and state high anxious participants, whereas P3 decreased in participants who reported a higher frequency of cognitive failures. Electrophysiological responses revealed that cognitive strategies were probably activated by more anxious and less self-confident individuals in order to be efficient in their performance. As shown by current research, frontal areas and anterior cingulated cortex appear to be particularly involved in this affective-cognitive interaction.

A new standardized set of ecological pictures for experimental and clinical research on visual object processing

A new set of 174 pictures in black-and-white, coloured and spatially filtered versions, taken from photographs of real objects belonging to different semantic categories, was realised for experimental and clinical research on visual object processing. Two samples, one of English speakers and one of Italian speakers, were tested in order to provide the normative data for each picture, in both black-and-white and coloured versions, in relation to familiarity, visual complexity and name agreement.

Fearful expressions enhance recognition memory: Electrophysiological evidence

Facial expressions play a key role in affective and social behavior. However, the temporal dynamics of the brain responses to emotional faces remain still unclear, in particular an open question is at what stage of face processing expressions might influence encoding and recognition memory. To try and answer this question we recorded the event-related potentials (ERPs) elicited in an old/new recognition task. A novel aspect of the present design was that whereas faces were presented during the study phase with either a happy, fearful or neutral expression, they were always neutral during the memory retrieval task. The ERP results showed three main findings: An enhanced early fronto-central positivity for faces encoded as fearful, both during the study and the retrieval phase. During encoding subsequent memory (Dm effect) was influenced by emotion. At retrieval the early components P100 and N170 were modulated by the emotional expression of the face at the encoding phase. Finally, the later ERP components related to recognition memory were modulated by the previously encoded facial expressions. Overall, these results suggest that face recognition is modulated by top-down influences from brain areas associated with emotional memory, enhancing encoding and retrieval in particular for fearful emotional expressions.

Alpha waves: a neural signature of visual suppression

Alpha waves are traditionally considered a passive consequence of the lack of stimulation of sensory areas. However, recent results have challenged this view by showing a modulation of alpha activity in cortical areas representing unattended information during active tasks. These data have led us to think that alpha waves would support a ‘gating function’ on sensorial stimulation that actively inhibits unattended information in attentional tasks. Visual suppression occurring during a saccade and blink entails an inhibition of incoming visual information, and it seems to occur at an early processing stage. In this study, we hypothesized that the neural mechanism through which the visual system exerts this inhibition is the active imposition of alpha oscillations in the occipital cortex, which in turn predicts an increment of alpha amplitude during a visual suppression phenomena. We measured visual suppression occurring during short closures of the eyelids, a situation well suited for EEG recordings and stimulated the retinae with an intra-oral light administered through the palate. In the behavioral experiment, detection thresholds were measured with eyes steady open and steady closed, showing a reduction of sensitivity in the latter case. In the EEG recordings performed under identical conditions we found stronger alpha activity with closed eyes. Since the stimulation does not depend on whether the eyes were open or closed, we reasoned that this should be a central effect, probably due to a functional role of alpha oscillation in agreement with the ‘gating function’ theory.

Emotions shape memory suppression in trait anxiety

The question that motivated this study was to investigate the relation between trait anxiety, emotions and memory control. To this aim, memory suppression was explored in high and low trait anxiety individuals with the Think/No-think paradigm. After learning associations between neutral words and emotional scenes (negative, positive, and neutral), participants were shown a word and were requested either to think about the associated scene or to block it out from mind. Finally, in a test phase, participants were again shown each word and asked to recall the paired scene. The results show that memory control is influenced by high trait anxiety and emotions. Low trait anxiety individuals showed a memory suppression effect, whereas there was a lack of memory suppression in high trait anxious individuals, especially for emotionally negative scenes. Thus, we suggest that individuals with anxiety may have difficulty exerting cognitive control over memories with a negative valence. These findings provide evidence that memory suppression can be impaired by anxiety thus highlighting the crucial relation between cognitive control, emotions, and individual differences in regulating emotions.

Attractiveness and affordance shape tools neural coding: insight from ERPs.

The relation between attractiveness and motor affordance is a key topic in design and has not yet been investigated electrophysiologically. In this respect, action affordance and attractiveness represent two crucial dimensions in object processing (specifically for tools). In light of this evidence, Event Related Potentials (ERPs) enabled us to gain new insights into the time course of the interaction between these two dimensions during an explicit tool evaluation task. Behaviorally, tools that were judged as high affording and high attractive yielded faster response times than those judged as low affording and low attractive. The ERP results showed that early processes related to sensory gating and feature extraction (N100) were sensitive to both affordance and attractiveness; the P200 was dominated by affordance, indexing a facilitated access to motor action representation. The N300, P300 and the Late Positive Potential (LPP) showed enhanced responses for highly affording/attractive tools, reflecting the interconnection between attractiveness and affordance. Later responses were entirely affected by attractiveness, suggesting additional affective responses evoked by desirable tools. We are showing that things that are perceived as more functional and attractive have a privileged neural activation in the time course of tool evaluation, for the first time.

Recognition of category-related visual stimuli in Parkinson's disease : Before and after pharmacological treatment

Visual-sensory dysfunctions and semantic processing impairments are widely reported in Parkinsons disease (PD) research. The present study investigated the category-specific deficit in object recognition as a function of both the semantic category and spatial frequency content of stimuli. In the first experiment, the role of dopamine in object-recognition processing was assessed by comparing PD drug naïve (PD-DN), PD receiving levodopa treatment (PD-LD), and control subjects. Experiment 2 consisted of a retest session for PD drug naïve subjects after a period of pharmacological treatment. All participants completed an identification task which displayed animals and tools at nine levels of filtering. Each object was revealed in a sequence of frames whereby the object was presented at increasingly less-filtered images up to a complete version of the image. Results indicate an impaired identification pattern for PD-DN subjects solely for animal category stimuli. This differential pharmacological therapy effect was also confirmed at retest (experiment 2). Thus, our data suggest that dopaminergic loss has a specific role in category-specific impairment. Two possible hypotheses are discussed that may account for the defective recognition of semantically different objects in PD.

Visual Recognition Memory in Alzheimer's Disease: Repetition-Lag Effects

There is considerable evidence that visual recognition memory is largely affected by Alzheimers disease (AD). Deficits might concern the forming, maintaining, and matching of the memory representation of the visual stimulus, especially when long interitem lags occur. The aim of the present study was to assess the effect of repetition lag on picture identification in mild- and moderate-AD patients, as well as in elderly controls. Participants underwent an old/new paradigm. To manipulate the temporal gradient, short and long lags were introduced between the first and second presentations. Pictures were presented at different levels of spatial filtering, following a coarse-to-fine order. This allowed for the measurement of the amount of physical information required for the identification of stimuli as a function of prior exposure and repetition lag. In the elderly, the magnitude of repetition priming did not differ as a function of interitem lag. Instead, repetition-lag effects interacted with dementia severity, and the capacity to retain memory traces for longer intervals worsened as the disease progresses. Current findings suggest that severe cortical degeneration may render AD patients unable to maintain their perceptual memories, and that dementia severity is a critical variable in the visual recognition memory assessment.

You are that smiling guy I met at the party! Socially positive signals foster memory for identities and contexts.

The emotional influence of facial expressions on memory is well-known whereas the influence of emotional contextual information on memory for emotional faces is yet to be extensively explored. This study investigated the interplay between facial expression and the emotional surrounding context in affecting both memory for identities (item memory) and memory for associative backgrounds (source memory). At the encoding fearful and happy faces were presented embedded in fear or happy scenes (i.e.: fearful faces in fear-scenes, happy faces in happy-scenes, fearful faces in happy-scenes and happy faces in fear-scenes) and participants were asked to judge the emotional congruency of the face-scene compounds (i.e. fearful faces in fear-scenes and happy faces in happy-scenes were congruent compounds). In the recognition phase, the old faces were intermixed with the new ones: all the faces were presented isolated with a neutral expression. Participants were requested to indicate whether each face had been previously presented (item memory). Then, for each old face the memory for the scene originally compounded with the face was tested by a three alternative forced choice recognition task (source memory). The results evidenced that face identity memory is differently modulated by the valence in congruent face-context compounds with better identity recognition (item memory) for happy faces encoded in happy-scenarios. Moreover, also the memory for the surrounding context (source memory) benefits from the association with a smiling face. Our findings highlight that socially positive signals conveyed by smiling faces may prompt memory for identity and context.

Time perception impairment in early-to-moderate stages of Huntington’s disease is related to memory deficits

Huntington’s disease (HD) primarily affects striatum and prefrontal dopaminergic circuits which are fundamental neural correlates of the timekeeping mechanism. The few studies on HD mainly investigated motor timing performance in second durations. The present work explored time perception in early-to-moderate symptomatic HD patients for seconds and milliseconds with the aim to clarify which component of the scalar expectancy theory (SET) is mainly responsible for HD timing defect. Eleven HD patients were compared to 11 controls employing two separate temporal bisection tasks in second and millisecond ranges. Our results revealed the same time perception deficits for seconds and milliseconds in HD patients. Time perception impairment in early-to-moderate stages of Huntington’s disease is related to memory deficits. Furthermore, both the non-systematical defect of temporal sensitivity and the main impairment of timing performance in the extreme value of the psychophysical curves suggested an HD deficit in the memory component of the SET. This result was further confirmed by the significant correlations between time perception performance and long-term memory test scores. Our findings added important preliminary data for both a deeper comprehension of HD time-keeping deficits and possible implications on neuro-rehabilitation practices.