Riccardo Brunetti

Heart rate and heart rate variability modification in chronic insomnia patients.

Chronic insomnia is highly prevalent in the general population, provoking personal distress and increased risk for psychiatric and medical disorders. Autonomic hyper-arousal could be a pathogenic mechanism of chronic primary insomnia. The aim of this study was to investigate autonomic activity in patients with chronic primary insomnia by means of heart rate variability (HRV) analysis. Eighty-five consecutive patients affected by chronic primary insomnia were enrolled (38 men and 47 women; mean age: 53.2 ± 13.6). Patients were compared with a control group composed of 55 healthy participants matched for age and gender (23 men and 32 women; mean age: 54.2 ± 13.9). Patients underwent an insomnia study protocol that included subjective sleep evaluation, psychometric measures, and home-based polysomnography with evaluation of HRV in wake before sleep, in all sleep stages, and in wake after final awakening. Patients showed modifications of heart rate and HRV parameters, consistent with increased sympathetic activity, while awake before sleep and during Stage-2 non-REM sleep. No significant differences between insomniacs and controls could be detected during slow-wave sleep, REM sleep, and post-sleep wake. These results are consistent with the hypothesis that autonomic hyper-arousal is a major pathogenic mechanism in primary insomnia, and confirm that this condition is associated with an increased cardiovascular risk.

Memories of attachment hamper EEG cortical connectivity in dissociative patients

In this study, we evaluated cortical connectivity modifications by electroencephalography (EEG) lagged coherence analysis, in subjects with dissociative disorders and in controls, after retrieval of attachment memories. We asked thirteen patients with dissociative disorders and thirteen age- and sex-matched healthy controls to retrieve personal attachment-related autobiographical memories through adult attachment interviews (AAI). EEG was recorded in the closed eyes resting state before and after the AAI. EEG lagged coherence before and after AAI was compared in all subjects. In the control group, memories of attachment promoted a widespread increase in EEG connectivity, in particular in the high-frequency EEG bands. Compared to controls, dissociative patients did not show an increase in EEG connectivity after the AAI. Conclusions: These results shed light on the neurophysiology of the disintegrative effect of retrieval of traumatic attachment memories in dissociative patients.

eCorsi: implementation and testing of the Corsi block-tapping task for digital tablets.

The Corsi block-tapping task is a widely used test to assess visuo-spatial working memory. The test is traditionally administered using nine square blocks positioned on a wooden board, but numerous digital versions have been developed. In this study, we tested one-hundred and seven participants divided into two age groups (18–30 and over 50) in forward, backward and supraspan-forward conditions with eCorsi, a tablet version of the Corsi task. Compared to the traditional physical board, eCorsi has several advantages, including: simple installation, set-up, and use; considerably increased accuracy in presentation timing, automatic measures of span and reaction times, in both the forward and backward response modalities. Results showed that average span and error rates were essentially analogous to the ones obtained in the main standardization studies, which have used the original physical version of the Corsi test. Furthermore, timing results provide new indications about the mechanisms underlying spatial sequence processing, suggesting that the subjects response is not planned during sequence presentation, but between the end of the presentation and the beginning of the response.

Modifications of EEG power spectra in mesial temporal lobe during n-back tasks of increasing difficulty. A sLORETA study

The n-back task is widely used to investigate the neural basis of Working Memory (WM) processes. The principal aim of this study was to explore and compare the EEG power spectra during two n-back tests with different levels of difficulty (1-back vs. 3-back). Fourteen healthy subjects were enrolled (seven men and seven women, mean age 31.21 ± 7.05 years, range: 23–48). EEG was recorded while performing the N-back test, by means of 19 surface electrodes referred to joint mastoids. EEG analysis were conducted by means of the standardized Low Resolution brain Electric Tomography (sLORETA) software. The statistical comparison between EEG power spectra in the two conditions was performed using paired t-statistics on the coherence values after Fishers z transformation available in the LORETA program package. The frequency bands considered were: delta (0.5–4 Hz); theta (4.5–7.5 Hz); alpha (8–12.5 Hz); beta (13–30 Hz); gamma (30.5–100 Hz). Significant changes occurred in the delta band: in the 3-back condition an increased delta power was localized in a brain region corresponding to the Brodmann Area (BA) 28 in the left posterior entorhinal cortex (T = 3.112; p < 0.05) and in the BA 35 in the left perirhinal cortex in the parahippocampal gyrus (T = 2.876; p < 0.05). No significant differences were observed in the right hemisphere and in the alpha, theta, beta, and gamma frequency bands. Our results indicate that the most prominent modification induced by the increased complexity of the task occur in the mesial left temporal lobe structures.

The impact of cross-modal correspondences on working memory performance.

Cross-modal correspondences influence perceptual performance in adults, infants, and even nonhuman primates across a variety of different sensory modalities, including tasks involving speeded detection and categorization. However, to date, it is still unclear whether and how correspondences could modulate post-perceptual processes, such as working memory (WM). We investigated this issue using an audiovisual two-back task. In Experiment 1, 3 kinds of correspondences were used: audio/visual numerosity, pitch/shape, and pitch/elevation, each presented congruently (e.g., for numerosity: 3 tones along with 3 shapes) or incongruently (3 tones/2 shapes). Participants attended to the visual or auditory modalities, or both, simultaneously. The results revealed faster target-detection latencies following congruent as compared to incongruent stimulation, especially for numerosity congruence. In Experiment 2, we focused on numerosity, varying the correspondence of the unattended modality, thus having correspondences at both sample (e.g., 3 tones/3 shapes) and target (e.g., 3 tones/3 shapes), only at sample (sample: 3 tones/3 shapes; target: 3 tones/2 shapes), only at target (sample: 3 tones/2 shapes; target: 3 tones/3 shapes), or never. To investigate the information format we included “symbolic” quantities (i.e., visually/auditorily presented digits). The results confirmed the congruence effects, specifically when the correspondence operates at the target display, thus affecting response selection. The experiment revealed modal effects, showing how task-irrelevant digits affect performance only in the auditory modality, while task-irrelevant quantities affect it only when presented visually. Overall, these findings highlight the impact of cross-modal correspondences on WM, adding new light on the link between perceptual and post-perceptual stages of human information processing.

Default Mode Network alterations in alexithymia: an EEG power spectra and connectivity study

Recent neuroimaging studies have shown that alexithymia is characterized by functional alterations in different brain areas [e.g., posterior cingulate cortex (PCC)], during emotional/social tasks. However, only few data are available about alexithymic cortical networking features during resting state (RS). We have investigated the modifications of electroencephalographic (EEG) power spectra and EEG functional connectivity in the default mode network (DMN) in subjects with alexithymia. Eighteen subjects with alexithymia and eighteen subjects without alexithymia matched for age and gender were enrolled. EEG was recorded during 5 min of RS. EEG analyses were conducted by means of the exact Low Resolution Electric Tomography software (eLORETA). Compared to controls, alexithymic subjects showed a decrease of alpha power in the right PCC. In the connectivity analysis, compared to controls, alexithymic subjects showed a decrease of alpha connectivity between: (i) right anterior cingulate cortex and right PCC, (ii) right frontal lobe and right PCC, and (iii) right parietal lobe and right temporal lobe. Finally, mediation models showed that the association between alexithymia and EEG connectivity values was directed and was not mediated by psychopathology severity. Taken together, our results could reflect the neurophysiological substrate of some core features of alexithymia, such as the impairment in emotional awareness.

Neurophysiological correlates of eye movement desensitization and reprocessing sessions: preliminary evidence for traumatic memories integration.

We have investigated the potential role of eye movement desensitization and reprocessing (EMDR) in enhancing the integration of traumatic memories by measuring EEG coherence, power spectra and autonomic variables before (pre‐EMDR) and after (post‐EMDR) EMDR sessions during the recall of patients traumatic memory. Thirteen EMDR sessions of six patients with post‐traumatic stress disorder were recorded. EEG analyses were conducted by means of the standardized Low Resolution Electric Tomography (sLORETA) software. Power spectra, EEG coherence and heart rate variability (HRV) were compared between pre‐ and post‐EMDR sessions. After EMDR, we observed a significant increase of alpha power in the left inferior temporal gyrus (T = 3·879; P = 0·041) and an increased EEG coherence in beta band between C3 and T5 electrodes (T = 6·358; P<0·001). Furthermore, a significant increase of HRV in the post‐EMDR sessions was also observed (pre‐EMDR: 6·38 ± 6·83; post‐EMDR: 2·46 ± 2·95; U‐Test= 45, P = 0·043). Finally, the values of lagged coherence were negatively associated with subjective units of disturbance (r(24) = −0·44, P<0·05) and positively associated with parasympathetic activity (r(24)=0·40, P<0·05). Our results suggest that EMDR leads to an integration of dissociated aspects of traumatic memories and, consequently, a decrease of hyperarousal symptoms [Correction made here after initial publication].

Are crossmodal correspondences relative or absolute? Sequential effects on speeded classification

Crossmodal correspondences have often been demonstrated using congruency effects between pairs of stimuli in different sensory modalities that vary along separate dimensions. To date, however, it is still unclear the extent to which these correspondences are relative versus absolute in nature: that is, whether they result from pre-defined values that rigidly link the two dimensions or rather result from flexible values related to the previous occurrence of the crossmodal stimuli. Here, we investigated this issue in a speeded classification task featuring the correspondence between auditory pitch and visual size (e.g., congruent correspondence between high pitch/small disc and low pitch/large disc). Participants classified the size of the visual stimuli (large vs. small) while hearing concurrent high- or low-pitched task-irrelevant sounds. On some trials, visual stimuli were paired instead with “intermediate” pitch, that could be interpreted differently according to the auditory stimulus on the preceding trial (i.e., as “lower” following the presentation of a high pitch tone, but as “higher” following the presentation of a low pitch tone). Performance on sequence-congruent trials (e.g., when a small disc paired with the intermediate-pitched tone was preceded by a low pitch tone) was compared to sequence-incongruent trials (e.g., when a small disc paired with the intermediate-pitch tone was by a high-pitched tone). The results revealed faster classification responses on sequence-congruent than on sequence-incongruent trials. This demonstrates that the effect of the pitch/size correspondence is relative in nature, and subjected to trial-by-trial interpretation of the stimulus pair.

Cross-modal and intra-modal binding between identity and location in spatial working memory: The identity of objects does not help recalling their locations

In this study we tested incidental feature-to-location binding in a spatial task, both in unimodal and cross-modal conditions. In Experiment 1 we administered a computerised version of the Corsi Block-Tapping Task (CBTT) in three different conditions: the first one analogous to the original CBTT test; the second one in which locations were associated with unfamiliar images; the third one in which locations were associated with non-verbal sounds. Results showed no effect on performance by the addition of identity information. In Experiment 2, locations on the screen were associated with pitched sounds in two different conditions: one in which different pitches were randomly associated with locations and the other in which pitches were assigned to match the vertical position of the CBTT squares congruently with their frequencies. In Experiment 2 we found marginal evidence of a pitch facilitation effect in the spatial memory task. We ran a third experiment to test the same conditions of Experiment 2 with a within-subject design. Results of Experiment 3 did not confirm the pitch–location facilitation effect. We concluded that the identity of objects does not affect recalling their locations. We discuss our results within the framework of the debate about the mechanisms of “what” and “where” feature binding in working memory.

Did I see your hand moving? The effect of movement-related information on the Corsi block tapping task

The Corsi Block Tapping Task is a widespread test used to assess spatial working memory. Previous research hypothesized that the discrepancy found in some cases between the traditional and the digital (touchscreen) version of the Corsi block tapping task may be due to a direct motor resonance between the experimenter’s and the participant’s hand movements. However, we hypothesize that this discrepancy might be due to extra movement-related information included in the traditional version, lacking in the digital one. We investigated the effects of such task-irrelevant information using eCorsi, a touchscreen version of the task. In Experiment 1, we manipulate timing in sequence presentation, creating three conditions. In the Congruent condition, the inter-stimulus intervals reflected the physical distance in which the stimuli were spatially placed: The longer the spatial distance, the longer the temporal interval. In the Incongruent condition the timing changed randomly. Finally, in the Isochronous condition every stimulus appeared after a fixed interval, independently from its spatial position. The results showed a performance enhancement in the Congruent condition, suggesting an incidental spatio-temporal binding. In Experiment 2, we added straight lines between each location in the sequences: In the Trajectories condition participants saw trajectories from one spatial position to the other during sequence presentation, while a condition without such trajectories served as control. Results showed better performances in the Trajectories condition. We suggest that the timing and trajectories information play a significant role in the discrepancies found between the traditional and the touchscreen version of the Corsi Block Tapping Task, without the necessity of explanations involving direct motor resonance (e.g. seeing an actual hand moving) as a causal factor.