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A cognitive neuroscientific model of impulsivity and anxiety

Final Report Summary - CNMIA (A cognitive neuroscientific model of impulsivity and anxiety)

In the last three years, I investigated left-right brain dynamics by focusing on the effects of attention on cerebral asymmetry in an auditory task with linguistic and emotional stimuli. I initiated the following experiments:

(1) A behavioural experiment that explored the effect of impulsivity and anxiety on hemispheric attention using dichotic listening to words and affects (DLWA)

The first step of this experiment was to demonstrate the importance of attention in assessing hemispheric specialisation for processing words and emotions. Thus, one paper drawn from this experiment, which is currently under review, examined the effects of attention on ear advantages using the DLWA, a focused-attention paradigm. We compared the mixed condition, in which attention is switched between the ears in each trial, to the blocked condition, in which attention is directed to one ear for an entire block of trials. Results showed a decreased right ear advantage for word processing only in the mixed condition and an increased left ear advantage for emotion processing in both attention conditions for hits index. The mixed condition showed smaller laterality effects than the blocked condition for words with respect to hit index, while increasing right ear predominance for intrusions. The greater percentage of intrusions in the right ear for the word task and in the mixed condition suggests that the right ear (left hemisphere (LH)) is most vulnerable to attention switching. We posit that the attention manipulation has a greater effect on word processing than on emotion processing and propose that ear advantages reflect a combination of the effects of attentional and structural constraints on lateralisation.

The second paper examined the effects of anxiety and impulsivity on hemispheric attention using DLWA. We found that both high anxiety and high impulsivity were associated with impaired overall accuracy (hits index), with general susceptibility to interference, with perceptual deficits in the LH and with decreased cognitive control in the right hemisphere (RH). Currently, I am working on resubmitting this paper.

This study makes two important contributions. First, the use of the both words and affects can add a great deal to our current understanding of the effects of attention on ear advantages, given that almost all of that research to date has used consonant-vowel syllables as stimuli. Secondly, it examines the effects of cognitive control on ear advantage, as intrusions from the unattended ear reflect failures of cognitive control. This has implications for the use of DL when studying attentional control in both normal and clinical subgroups.

(2) An electroencephalogram (EEG) study on a young adult with left hemispherectomy

The experiment examined RH recovery of language processing using words with emotional prosodies. We concluded that the isolated RH of the patient has some ability to process and discriminate phonetic information. Behavioural results showed better performance in the words spoken in neutral than sad tone of voice. Also, the contralateral projection (i.e. focused attention to the left ear) was stronger in both neutral and sad prosodies. Electrophysiological results showed larger amplitudes over the right frontal area in the left than in the right ear for neutral prosody, and smaller ear difference in amplitudes for the sad prosody. There were also stronger and clearer differences in amplitudes over the right frontal area between the two prosodies in the left than in the right ear (ipsilateral to the RH).

Based on the behavioural and physiological results, neutral stimuli in the left ear (contralateral to the intact RH) had the highest sensitivity and the largest event-related potential (ERP) component amplitudes. We concluded that the isolated RH of the participant has some ability to process and discriminate phonetic information (stop consonants), suggesting that language recovery in the RH reflected the strategy used by the LH in an intact brain.

This paper is in preparation before publication.

(3) A combined functional magnetic resonance imaging (fMRI) with EEG measures of hemispheric activation in order to study the effect of emotional prosody on hemispheric specialisation to words

I completed a draft of the results of the EEG experiment for publication. I analysed the relationships between hemispheric specialisation and interaction, using several behavioural indices of the ear advantage, involving accuracy and latency as well as electrophysiological measures. In this study, nine electrodes were chosen out of 64 electrode sites corresponding to frontal, central, temporal, and parietal regions of interest, covering a number of areas, suggested by dichotic listening studies to be central for words and emotions processing:

(a) frontal: F3, F4;
(b) central: Cz, C3, C4;
(c) fronto-temporal: T7, T8; and
(d) parietal: P7, P8.

This montage provided coverage of left- and right-hemisphere activity in both anterior and posterior regions.

ERP averaging:
ERP waveforms were averaged both within and across participants, separately for electrode site (frontal, fronto-temporal, central, parietal), hemisphere (left, right), ear of stimulus presentation (left, right), and prosody (neutral, negative). The ERP waveforms presented in this study are averages of correctly detected target items (hits). The ERP recorded in response to the dichotic presentation of the emotionally charged words (neutral, sad). The time windows were chosen to represent the major peaks of the responses observed in the green fluorescent protein (GFP). Accordingly, early and late waves were studied in two time windows: 150 - 170 ms and 240 - 260 ms. We also used LORETA source localisation method from the electrophysiological data.

Behavioural results showed:

(a) general susceptibility to interference for words in sad prosody;
(b) better perceptual processes in the LH;
(c) decreased cognitive control in the LH;
(d) at the group analysis level, high impulsivity showed better performance of the right ear (enhanced LH) in word in sad than neutral prosody. Low impulsivity showed no significant difference between the two ears in both neutral and sad prosody.

Electrophysiological results showed:

(a) greater activity in the frontal, temporal and parietal regions for words in neutral than sad prosody in early-time window, as opposed to greater activity for words in sad than neutral prosody in late time window, suggesting different pattern of information processing for words in negative emotional tone of voice;
(b) biliateral activity over the frontal cortex and unilateral activity over the LH for parietal and temporal cortex for words in both neutral and sad prosody, suggesting that words processing extend auditory cortex and involved cognitive network;
(c) groups differences in the sub-genual cortex (part of the VMPFC; BA25) activation in time window of 150 - 170 ms showed biliateral activity for word target spoken in neutral prosody when attention was directed to either the left or right ear.

The low impulsivity group shows higher activation relative to the high impulsivity group. For words in sad prosody, the low impulsivity group showed attenuated higher activation in the hemisphere ipsilateral to the stimuli presentation, while the high impulsivity group showed higher activation in the hemisphere contralateral to the stimuli presentation.

Currently, I am analysing the data of the structural MRI (sMRI) / fMRI in preparation for separate publication.

Through the broad interdisciplinary training in the cognitive neuroscience laboratory of Professor Zaidel in the Department of Psychology at UCLA, I acquired an exceptionally strong theoretical and methodological background in behavioural laterality experiments. I had numerous research opportunities during this intense training period. These included my investigations into left-right brain dynamics in impulsivity and anxiety by focusing on the effects of attention on cerebral asymmetry. I also initiated an investigation into the physiological correlates of hemispheric asymmetry and interhemispheric interaction in impulsivity and anxiety using integrated personality measures, auditory behavioural laterality and physiological and anatomical measures. As an extensive part of my training, I learned to collect cutting-edge high density EEG and ERP data from an individual while that individual engaged in a range of behavioural laterality experiments. Funded by the UCLA General Clinical Research (GCRC), I collected both fMRI and structural MRI data of the whole brain (sMRI). I also completed a very unique study involving the co-registration of fMRI and EEG on the effect of attention on hemispheric specialisation in dichotic listening task to emotional words. This was an exceptional opportunity because the simultaneous recording of these two different data types is available in only a few research sites world-wide. As a part of my training, I also conducted an EEG case study on a young adult who experienced a left hemispherectomy. This study investigated the RH recovery of language processing following this extreme type of lesion. Our results indicated that language recovery in the RH reflects a strategy typically used by the LH in an intact brain. Obviously, such studies lead to new and exciting questions that will drive many of my future research efforts.

My long-term goals are to develop the theoretical insights from this groundbreaking, multi-disciplinary research. The future breakthroughs in this field are clearly to multi-disciplinary approaches. My interest lies in exploring the atypical asymmetry within impulsivity and anxiety in relation to attention, and reformulating those two traits in terms of hemisphere specialisation, hemispheric connectivity, and the relation between the hemispheres. These are areas I worked on extensively during my period at UCLA. It is my ambition to pursue further this work in Israel. For that purpose, I applied for funding from the Israel Science Foundation (ISF) in November 2012. I also am planning to apply for funds from the European Commission (EC) to conduct pilot studies using MRI technology combined with EEG / ERP and magnetoencephalography (MEG) technology. I believe that by combining my background as a clinical criminologist and therapist with cognitive neuroscience, I will be better able to develop more effective strategies for the treatment and rehabilitation of a wide range of cognitive and behavioural problems associated with impulsivity and impulsivity-related disorders. One such approach I am considering is the use of neuro-feedback that takes into account behavioural, cognitive, subjective and brain measures. This could lead to the development of a programme in which neural feedback is used to improve attention and self-control (e.g. impulsivity, anxiety, ADHD) to ultimately lead to more normalised behaviours.