Response-Modality-Specific Encoding of Human Choices in Upper Beta Band Oscillations during Vibrotactile Comparisons

Perceptual decisions based on the comparison of two vibrotactile frequencies have been extensively studied in non-human primates. Recently, we obtained corresponding findings from human oscillatory electroencephalography (EEG) activity in the form of choice-selective modulations of upper beta band amplitude in medial premotor areas. However, the research in non-human primates as well as its human counterpart was so far limited to decisions reported by button presses. Thus, here we investigated whether the observed human beta band modulation is specific to the response modality. We recorded EEG activity from participants who compared two sequentially presented vibrotactile frequencies (f1 and f2), and decided whether f2 > f1 or f2 < f1, by performing a horizontal saccade to either side of a computer screen. Contrasting time-frequency transformed EEG data between both choices revealed that upper beta band amplitude (∼24–32 Hz) was modulated by participants’ choices before actual responses were given. In particular, “f2 > f1” choices were always associated with higher beta band amplitude than “f2 < f1” choices, irrespective of whether the choice was correct or not, and independent of the specific association between saccade direction and choice. The observed pattern of beta band modulation was virtually identical to our previous results when participants responded with button presses. In line with an intentional framework of decision making, the most likely sources of the beta band modulation were now, however, located in lateral as compared to medial premotor areas including the frontal eye fields. Hence, we could show that the choice-selective modulation of upper beta band amplitude is on the one hand consistent across different response modalities (i.e., same modulation pattern in similar frequency band), and on the other hand effector specific (i.e., modulation originating from areas involved in planning and executing saccades)

Response modality-dependent categorical choice representations for vibrotactile comparisons

Previous electrophysiological studies in monkeys and humans suggest that premotor regions are the primary loci for the encoding of perceptual choices during vibrotactile comparisons. However, these studies employed paradigms wherein choices were inextricably linked with the stimulus order and selection of manual movements. It remains largely unknown how vibrotactile choices are represented when they are decoupled from these sensorimotor components of the task. To address this question, we used fMRI-MVPA and a variant of the vibrotactile frequency discrimination task which enabled the isolation of choice-related signals from those related to stimulus order and selection of the manual decision reports. We identified the left contralateral dorsal premotor cortex (PMd) and intraparietal sulcus (IPS) as carrying information about vibrotactile choices. Our finding provides empirical evidence for an involvement of the PMd and IPS in vibrotactile decisions that goes above and beyond the coding of stimulus order and specific action selection. Considering findings from recent studies in animals, we speculate that the premotor region likely serves as a temporary storage site for information necessary for the specification of concrete manual movements, while the IPS might be more directly involved in the computation of choice. Moreover, this finding replicates results from our previous work using an oculomotor variant of the task, with the important difference that the informative premotor cluster identified in the previous work was centered in the bilateral frontal eye fields rather than in the PMd. Evidence from these two studies indicates that categorical choices in human vibrotactile comparisons are represented in a response modality-dependent manner

Decoding working memory and perceptual choice during tactile information processing

Working memory and decision-making are two building blocks of human cog-nition that are involved in most goal-directed behaviors. Exposing the neural underpinnings of these mental functions has been a central goal of cognitive and systems neuroscience. Critically, most models and theories have emerged from empirical findings in the visual domain, leaving open the question of whether they hold for other sensory domains. In this dissertation, I aimed at studying the neural correlates of working memory and decision-making during tactile information processing. In particular, I con-ducted four fMRI studies to address the question of which brain regions repre-sent the contents of working memory and perceptual choices. We found para-metric working memory representation of vibrotactile frequencies distributed across sensory, posterior parietal, and frontal cortices. This finding was also replicated in the visual and auditory modalities. Perceptual choices are repre-sented in the prefrontal and oculomotor regions, even when decoupled from saccade plans. These results support the view that the loci of mental representations depend critically on task requirements and content types

Gamma and Beta Oscillations in Human MEG Encode the Contents of Vibrotactile Working Memory

Ample evidence suggests that oscillations in the beta band represent quantitative information about somatosensory features during stimulus retention. Visual and auditory working memory (WM) research, on the other hand, has indicated a predominant role of gamma oscillations for active WM processing. Here we reconciled these findings by recording whole-head magnetoencephalography during a vibrotactile frequency comparison task. A Braille stimulator presented healthy subjects with a vibration to the left fingertip that was retained in WM for comparison with a second stimulus presented after a short delay. During this retention interval spectral power in the beta band from the right intraparietal sulcus and inferior frontal gyrus (IFG) monotonically increased with the to-be-remembered vibrotactile frequency. In contrast, induced gamma power showed the inverse of this pattern and decreased with higher stimulus frequency in the right IFG. Together, these results expand the previously established role of beta oscillations for somatosensory WM to the gamma band and give further evidence that quantitative information may be processed in a fronto-parietal network

Gamma Band Oscillation Response to Somatosensory Feedback Stimulation Schemes Constructed on Basis of Biphasic Neural Touch Representation

abstract: Prosthetic users abandon devices due to difficulties performing tasks without proper graded or interpretable feedback. The inability to adequately detect and correct error of the device leads to failure and frustration. In advanced prostheses, peripheral nerve stimulation can be used to deliver sensations, but standard schemes used in sensorized prosthetic systems induce percepts inconsistent with natural sensations, providing limited benefit. Recent uses of time varying stimulation strategies appear to produce more practical sensations, but without a clear path to pursue improvements. This dissertation examines the use of physiologically based stimulation strategies to elicit sensations that are more readily interpretable. A psychophysical experiment designed to investigate sensitivities to the discrimination of perturbation direction within precision grip suggests that perception is biomechanically referenced: increased sensitivities along the ulnar-radial axis align with potential anisotropic deformation of the finger pad, indicating somatosensation uses internal information rather than environmental. Contact-site and direction dependent deformation of the finger pad activates complimentary fast adapting and slow adapting mechanoreceptors, exhibiting parallel activity of the two associate temporal patterns: static and dynamic. The spectrum of temporal activity seen in somatosensory cortex can be explained by a combined representation of these distinct response dynamics, a phenomenon referred in this dissertation to “biphasic representation.” In a reach-to-precision-grasp task, neurons in somatosensory cortex were found to possess biphasic firing patterns in their responses to texture, orientation, and movement. Sensitivities seem to align with variable deformation and mechanoreceptor activity: movement and smooth texture responses align with potential fast adapting activation, non-movement and coarse texture responses align with potential increased slow adapting activation, and responses to orientation are conceptually consistent with coding of tangential load. Using evidence of biphasic representations’ association with perceptual priorities, gamma band phase locking is used to compare responses to peripheral nerve stimulation patterns and mechanical stimulation. Vibrotactile and punctate mechanical stimuli are used to represent the practical and impractical percepts commonly observed in peripheral nerve stimulation feedback. Standard patterns of constant parameters closely mimic impractical vibrotactile stimulation while biphasic patterns better mimic punctate stimulation and provide a platform to investigate intragrip dynamics representing contextual activation.Dissertation/ThesisDoctoral Dissertation Biomedical Engineering 201

Identifying a brain network for musical rhythm: A functional neuroimaging meta-analysis and systematic review

We conducted a systematic review and meta-analysis of 30 functional magnetic resonance imaging studies investigating processing of musical rhythms in neurotypical adults. First, we identified a general network for musical rhythm, encompassing all relevant sensory and motor processes (Beat-based, rest baseline, 12 contrasts) which revealed a large network involving auditory and motor regions. This network included the bilateral superior temporal cortices, supplementary motor area (SMA), putamen, and cerebellum. Second, we identified more precise loci for beat-based musical rhythms (Beat-based, audio-motor control, 8 contrasts) in the bilateral putamen. Third, we identified regions modulated by beat based rhythmic complexity (Complexity, 16 contrasts) which included the bilateral SMA-proper/pre-SMA, cerebellum, inferior parietal regions, and right temporal areas. This meta-analysis suggests that musical rhythm is largely represented in a bilateral cortico-subcortical network. Our findings align with existing theoretical frameworks about auditory-motor coupling to a musical beat and provide a foundation for studying how the neural bases of musical rhythm may overlap with other cognitive domains

Short-term memory of temporal aspects of noxious and innocuous thermal sensation : psychophysical and fMRI studies

La douleur peut être considérée comme un système de protection qui signale une menace et qui nous avertit des dégâts imminents aux tissus. En tant que mécanisme de défense, il nécessite l'apprentissage et la mémoire des expériences du passé pour la survie et les comportements liés à la douleur. Par conséquent, notre expérience de la douleur actuelle est fortement influencée par les expériences antérieures et l'apprentissage. Cependant, malgré son importance, notre compréhension actuelle de l'interaction entre le système de la douleur et le système de mémoire est très limitée. La mémoire de la douleur est un sujet de recherche très vaste. Il nécessite une compréhension des mécanismes impliqués à chaque étape du système de mémoire (mémoire immédiate, à court terme et à long terme) et l'interaction entre eux. Parmi les étapes multiples de la mémoire, la mémoire à court terme de la douleur est une zone qui est moins recherchée, alors qu'il existe une énorme quantité de recherche neuroscientifique dans la mémoire à court terme sur d'autres modalités, en particulier la vision. L'étude de la mémoire à court terme de la douleur est particulièrement importante car cette trace de la mémoire à court terme de la douleur est ensuite convertie en mémoire à long terme et affecte ensuite les expériences futures de la douleur. Cette thèse est largement axée sur la mémoire à court terme de la douleur. La complexité et la multi dimensionnalité de la douleur ajoutent encore un autre élément à la recherche sur la mémoire de la douleur. Par exemple, la trace de la mémoire de la douleur peut contenir des traces de mémoire de diverses composantes de la douleur telles que la réponse sensorielle affective, cognitive et motrice et l'interaction entre elles. Par conséquent, une première étape dans l'exploration neuroscientifique de la mémoire de la douleur nécessite la réduction de l'expérience de la douleur tout en englobant tous ces différents composants à un seul composant. Dans la recherche présentée ici, nous avons généralement examiné cela par des instructions d'attention ‘ top-down’ pour assister à la dimension sensorielle de la douleur. La recherche précédente sur la mémoire à court terme de la douleur a également porté principalement sur la dimension sensorielle de la douleur. Cependant, parmi les dimensions sensorielles de la douleur, la mémoire à court terme de l'intensité et de la dimension spatiale de la douleur a fait l'objet de recherches antérieures. Malgré son importance, la dimension temporelle de la douleur est restée complètement inexplorée dans la recherche sur la mémoire de la douleur. La recherche menée dans cette thèse est consacrée à l'exploration de la mémoire à court terme de la durée de la douleur. La durée de la douleur peut être suivie de manière indépendante, mais peut également être suivie conjointement avec la dimension d'intensité telle que le suivi dynamique de l'intensité de la douleur dans le temps. Les études menées dans cette thèse traitent spécifiquement du traitement isolé de la durée de la douleur ainsi que du traitement conjoint de la dimension durée / intensité de la douleur. La première étude psychophysique a exploré la nature de la représentation mentale du modèle de mémoire de la douleur thermique dynamique et a également été conçue pour aborder les différences de la dimension sensorielle et affective de la douleur thermique dans la mémoire à court terme. La deuxième étude psychophysique portait sur les propriétés de la mémoire à court terme de la sensation thermique non douloureux en comparant le suivi dynamique de la sensation et le suivi isolé de la durée d'un événement thermique non douloureux. La troisième étude poursuit l'exploration du traitement dynamique de la durée conjointement avec l'intensité par rapport au traitement isolé de la durée dans la mémoire à court terme en utilisant des stimuli thermiques douloureuse une résonance magnétique fonctionnelle (IRMF). Dans l'ensemble, les résultats des études psychophysiques ont montré une transformation significative de la durée et de la dynamique de la sensation thermique douloureux et non-douloureux dans la mémoire à court terme; comme la perte d'informations somatosensorielles temporelles en mémoire. Nous avons en outre montré une amélioration du rappel de la durée dans le suivi dynamique de la durée, en comparaison avec le suivi de la durée isolée. Nous avons également montré des différences dans les corrélats neuronaux de la mémoire à court terme de la durée de douleur par rapport à la dynamique de douleur. L'étude de l'IRMF a montré des similitudes frappantes dans les corrélats neuronaux sous-jacents à la mémoire à court terme de douleur et d'autres modalités telles que la contribution des coticés fronto-pariétales ainsi que les corticaux sensoriels impliqués dans le traitement perceptuel.Pain can be viewed as a protective system that signals threat and alerts us to impending tissue damage. As a defense mechanism, it necessitates the learning and memory of past painful experiences for survival and pain-related behavior. Therefore our current pain experience is heavily influenced by previous experiences and learning. However, despite its importance, our current understanding of the interaction between the pain system and the memory system is very limited. Pain memory is a very broad topic of research on its own. It requires an understanding of the mechanisms involved at each stage of the memory system (immediate, short-term, and long-term memory), and the interaction among them. Among the multiple stages of memory, the short-term memory of pain is an area that is less researched, while there are enormous amount of neuroscientific research in short-term memory of other modalities, particularly vision. Investigation of the short-term memory of pain is especially important as the short-term memory trace of pain is converted to long-term memory and subsequently affects future pain experiences. This thesis is broadly focused on the short-term memory of pain. The complexity and multi-dimensionality of pain adds yet another element to the research on pain memory. For example, the memory trace of pain may contain memory traces of various components of pain such as sensory, affective, cognitive, and motoric responses, and the interactions among them. Therefore, an initial step in the neuroscientific exploration of pain memory requires narrowing down the pain experience, which encompasses all of these various components, to one single component. In the research presented here, we achieved this using top-down attentional instructions to attend to the sensory component of pain. The previous research on short-term memory of pain also focused mainly on the sensory component of pain. However, within the sensory component of pain the short-term memory of intensity and spatial dimension of pain has been the focus of previous research. Despite its importance, the temporal dimension of pain remained completely unexplored in pain memory research. Thus, the research conducted in this thesis is devoted to the exploration of short-term memory of the duration of pain. Pain duration can be tracked independently, but it can also be tracked conjointly with intensity, such as in dynamic tracking of pain intensity over time. The studies addressed in this thesis examined the isolated processing of pain duration as well as conjoint processing of the duration and intensity of pain. The first psychophysical study explored the nature of the mental representation of the memory template of dynamic thermal pain sensation and, additionally, addressed the differences between the sensory versus affective dimensions of thermal pain sensation in short-term memory. The second psychophysical study focused on properties of the short-term memory of innocuous thermal sensation by comparing dynamic tracking of sensation versus isolated tracking of duration of an innocuous thermal event. The third study explored the dynamic processing of duration conjointly with intensity, versus the isolated processing of duration in short-term memory, using noxious thermal stimuli and functional magnetic resonance imaging (fMRI). Overall, the results of the psychophysical studies showed significant transformation of duration and dynamics information of noxious and innocuous thermal sensation in short-term memory, such as loss of temporal somatosensory information. Additionally, we showed improvement in duration recall during dynamic tracking versus isolated tracking of duration. The fMRI study revealed differences in neural correlates of short-term memory of pain duration versus pain dynamics. Importantly, it also showed striking similarities between neural correlates underlying the short-term memory of pain and those underlying other modalities, such as a contribution of fronto-parietal cortices as well as sensory cortices involved in perceptual processing

Neurophysiological correlates of preparation for action measured by electroencephalography

The optimal performance of an action depends to a great extend on the ability of a person to prepare in advance the appropriate kinetic and kinematic parameters at a specific point in time in order to meet the demands of a given situation and to foresee its consequences to the surrounding environment. In the research presented in this thesis, I employed high-density electroencephalography in order to study the neural processes underlying preparation for action. A typical way for studying preparation for action in neuroscience is to divide it in temporal preparation (when to respond) and event preparation (what response to make). In Chapter 2, we identified electrophysiological signs of implicit temporal preparation in a task where such preparation was not essential for the performance of the task. Electrophysiological traces of implicit timing were found in lateral premotor, parietal as well as occipital cortices. In Chapter 3, explicit temporal preparation was assessed by comparing anticipatory and reactive responses to periodically or randomly applied external loads, respectively. Higher (pre)motor preparatory activity was recorded in the former case, which resulted in lower post-load motor cortex activation and consequently to lower long-latency reflex amplitude. Event preparation was the theme of Chapter 4, where we introduced a new method for studying (at the source level) the generator mechanisms of lateralized potentials related to response selection, through the interaction with steady-state somatosensory responses. Finally, in Chapter 5 we provided evidence for the existence of concurrent and mutually inhibiting representations of multiple movement options in premotor and primary motor areas.EThOS - Electronic Theses Online ServiceGBUnited Kingdo