Estimating null and potent modes of feedforward communication in a computational model of cortical activity

Communication across anatomical areas of the brain is key to both sensory and motor processes. Dimensionality reduction approaches have shown that the covariation of activity across cortical areas follows well-delimited patterns. Some of these patterns fall within the "potent space" of neural interactions and generate downstream responses; other patterns fall within the "null space" and prevent the feedforward propagation of synaptic inputs. Despite growing evidence for the role of null space activity in visual processing as well as preparatory motor control, a mechanistic understanding of its neural origins is lacking. Here, we developed a mean-rate model that allowed for the systematic control of feedforward propagation by potent and null modes of interaction. In this model, altering the number of null modes led to no systematic changes in firing rates, pairwise correlations, or mean synaptic strengths across areas, making it difficult to characterize feedforward communication with common measures of functional connectivity. A novel measure termed the null ratio captured the proportion of null modes relayed from one area to another. Applied to simultaneous recordings of primate cortical areas V1 and V2 during image viewing, the null ratio revealed that feedforward interactions have a broad null space that may reflect properties of visual stimuli.

Studying peculiarities of variability of speech, language and motor processes in children with dysarthria

Introduction. The author investigates the problem of communicative development of children with dysarthria. The purpose of the research is to reveal the characteristic features of the variability of speech and motor processes in children with dysarthria (in particular, with a mild degree of pseudobulbar dysarthria) and to prove the existence of comorbidity levels of the disorders under study. Materials and Methods. The research is based on international and Russian refereed studies into language and speech, movements for organizing the communicative development of children with dysarthria (L. V. Lopatina, O. G. Prikhodko, T. V. Tumanova, T. B. Filicheva, G. V. Chirkina, Michael Robb, Kathleen Wermke). The research program was complemented by the application of an innovative technology based on biofeedback - Pablo System. The experimental study was conducted at preschool educational settings in Moscow (the Russian Federation). The sample consisted of 450 older preschool children with dysarthria (with a mild degree of pseudobulbar dysarthria) and a similar number of peers without speech disorders. Results. The article describes a modern interdisciplinary problem of studying speech and language and movement disorders in children with dysarthria (mild degree of pseudobulbar dysarthria, erased dysarthria, minimal dysarthric disorders) in the context of determining their codependency and conjugation. The study revealed variative characteristics of speech and language disorders and movement disorders in children with dysarthria. General and specific errors of speech and language and motor disorders in preschoolers of the experimental group were determined. The levels of comorbidity of speech-language and motor processes in children with dysarthria have been identified and scientifically substantiated. Conclusions. In conclusion, the author summarizes the main features of the variability of speech, language and motor processes in children with dysarthria.

Exploration of Relations between Belief-Tracking and Motor Processing using a new Ecologically-Valid Helping Task for Adults

<p>Three experiments investigated efficient belief tracking as described by the two-systems theory of human mindreading (Apperly & Butterfill, 2009) whereupon mindreading implies the operation of a flexible system that is slow to develop and cognitively effortful, and an efficient system which develops early but subject to signature limits. Signature limits have been evidenced by children’s and adults’ difficulty anticipating how someone with a false belief (FB) about an object’s identity, will act. In a recent investigation of signature limits, erroneous pre-activation of the motor system was detected when adults predicted the actions of an agent with an identity FB, suggesting that efficient mindreading and motor processes are linked (Edwards & Low, 2017). Moreover, young children differentiated between true and FBs about an object’s location, but not identity, as revealed by the object children retrieved in an active helping task (Fizke et al., 2017). The aim of the present thesis was to provide new evidence of signature limits in adults, and of the recent conjecture that efficient mindreading and motor processes interact. In helping tasks, participants’ interpretation of another’s actions is crucial to how they coordinate their helping response. Therefore, an ecologically valid helping task was adapted to investigate the proposed interface between efficient mindreading and motor processes. The present work measured adults’ eye movements made prior to helping, and their helping actions across a set of distinct directional full-body movements (around which side of a desk they swerved, which compartment they approached, toward which compartment they reached, and which object they retrieved). In this way, it was possible to investigate whether gaze direction correlated with full-body movements and whether adults’ gaze differed when the agent’s FB was about an object’s location or identity. Results from Experiment 1 indicated that efficient belief tracking is equipped to process location but not identity FBs, and that - in the location scenario - gaze direction correlated with the immediate stage of participants’ helping action (the direction they swerved). To investigate this correlation further, Experiment 2 drew upon research suggesting that temporarily tying an observer’s hands behind their backs impaired their ability to predict the outcome of hand actions (Ambrosini et al., 2012). Results showed that tying adults’ hands behind their back had a negative effect on their gaze behavior and severed the correlation between gaze and swerving, suggesting that the link between efficient mindreading and motor processes is fragile. Experiment 3 tested an alternative interpretation for Experiment 2’s findings (that restraining participants’ hands applied a domain-general distraction, rather than a specific detriment to belief tracking) by tying up participants’ feet. Results were ambiguous: the gaze behavior of participants whose feet were tied did not differ from those who were unrestrained, nor from those whose hands were bound. These findings support the two-systems theory and provide suggestive evidence of a connection between efficient mindreading and motor processes. However, the investigation highlights new methodological challenges for designing naturalistic helping tasks for adult participants.</p>

Exploration of Relations between Belief-Tracking and Motor Processing using a new Ecologically-Valid Helping Task for Adults

<p>Three experiments investigated efficient belief tracking as described by the two-systems theory of human mindreading (Apperly & Butterfill, 2009) whereupon mindreading implies the operation of a flexible system that is slow to develop and cognitively effortful, and an efficient system which develops early but subject to signature limits. Signature limits have been evidenced by children’s and adults’ difficulty anticipating how someone with a false belief (FB) about an object’s identity, will act. In a recent investigation of signature limits, erroneous pre-activation of the motor system was detected when adults predicted the actions of an agent with an identity FB, suggesting that efficient mindreading and motor processes are linked (Edwards & Low, 2017). Moreover, young children differentiated between true and FBs about an object’s location, but not identity, as revealed by the object children retrieved in an active helping task (Fizke et al., 2017). The aim of the present thesis was to provide new evidence of signature limits in adults, and of the recent conjecture that efficient mindreading and motor processes interact. In helping tasks, participants’ interpretation of another’s actions is crucial to how they coordinate their helping response. Therefore, an ecologically valid helping task was adapted to investigate the proposed interface between efficient mindreading and motor processes. The present work measured adults’ eye movements made prior to helping, and their helping actions across a set of distinct directional full-body movements (around which side of a desk they swerved, which compartment they approached, toward which compartment they reached, and which object they retrieved). In this way, it was possible to investigate whether gaze direction correlated with full-body movements and whether adults’ gaze differed when the agent’s FB was about an object’s location or identity. Results from Experiment 1 indicated that efficient belief tracking is equipped to process location but not identity FBs, and that - in the location scenario - gaze direction correlated with the immediate stage of participants’ helping action (the direction they swerved). To investigate this correlation further, Experiment 2 drew upon research suggesting that temporarily tying an observer’s hands behind their backs impaired their ability to predict the outcome of hand actions (Ambrosini et al., 2012). Results showed that tying adults’ hands behind their back had a negative effect on their gaze behavior and severed the correlation between gaze and swerving, suggesting that the link between efficient mindreading and motor processes is fragile. Experiment 3 tested an alternative interpretation for Experiment 2’s findings (that restraining participants’ hands applied a domain-general distraction, rather than a specific detriment to belief tracking) by tying up participants’ feet. Results were ambiguous: the gaze behavior of participants whose feet were tied did not differ from those who were unrestrained, nor from those whose hands were bound. These findings support the two-systems theory and provide suggestive evidence of a connection between efficient mindreading and motor processes. However, the investigation highlights new methodological challenges for designing naturalistic helping tasks for adult participants.</p>

Movement, Synchronization, and Partnering in Dance

In a neuroimaging study of tango dancers, the authors attempted to address two fundamental issues about dance: movement patterning (i.e., navigation of the legs in space) and synchronization of movement to the beat of music. The results of the study revealed the importance of the posterior parietal cortex to spatial navigation of movement and the cerebellum to synchronization to the beat. In a later two-person study of leading and following in dance, the author found that leaders accentuate motor processes, while followers accentuate sensory processes in their partnership. Dance is an interesting marriage of movement patterning, timing, and joint action.

Dual-Task Performance in Hearing-Impaired Older Adults—Study Protocol for a Cross-Sectional Mobile Brain/Body Imaging Study

Background: Hearing impairments are associated with reduced walking performance under Dual-task (DT) conditions. Little is known about the neural representation of DT performance while walking in this target group compared to healthy controls or younger adults. Therefore, utilizing the Mobile Brain/Body Imaging approach (MoBI), we aim at gaining deeper insights into the brain dynamics underlying the interaction of cognitive and motor processes during different DT conditions (visual and auditory) controlling for age and the potential performance decrements of older adults with hearing impairments.Methods: The cross-sectional study integrates a multifactorial mixed-measure design. Between-subject factors grouping the sample will be age (younger vs. older adults) and hearing impairment (mild vs. not hearing impaired). The within-subject factors will be the task complexity (single- vs. DT) and cognitive task modality (visual vs. auditory). Stimuli of the cognitive task will vary according to the stimulus modality (visual vs. auditory), presentation side (left vs. right), and presentation-response compatibility (ipsilateral vs. contralateral). Analyses of DT costs and underlying neuronal correlates focus either on gait or cognitive performance. Based on an a priori sample size calculation 96 (48 healthy and 48 mildly hearing impaired) community-dwelling older adults (50–70 years) and 48 younger adults (20–30 years) will be recruited. Gait parameters of speed and rhythm will be captured. EEG activity will be recorded using 64 active electrodes.Discussion: The study evaluates cognitive-motor interference (CMI) in groups of young and older adults as well as older adults with hearing impairment. The underlying processes of the interaction between motor and cognitive tasks will be identified at a behavioral and neurophysiological level comparing an auditory or a visual secondary task. We assume that performance differences are linked to different cognitive-motor processes, i.e., stimulus input, resource allocation, and movement execution. Moreover, for the different DT conditions (auditory vs. visual) we assume performance decrements within the auditory condition, especially for older, hearing-impaired adults. Findings will provide evidence of general mechanisms of CMI (ST vs. DT walking) as well as task-specific effects in dual-task performance while over ground walking.

Feedback and Feedforward Auditory-Motor Processes for Voice and Articulation in Parkinson's Disease

Purpose Unexpected and sustained manipulations of auditory feedback during speech production result in “reflexive” and “adaptive” responses, which can shed light on feedback and feedforward auditory-motor control processes, respectively. Persons with Parkinson's disease (PwPD) have shown aberrant reflexive and adaptive responses, but responses appear to differ for control of vocal and articulatory features. However, these responses have not been examined for both voice and articulation in the same speakers and with respect to auditory acuity and functional speech outcomes (speech intelligibility and naturalness). Method Here, 28 PwPD on their typical dopaminergic medication schedule and 28 age-, sex-, and hearing-matched controls completed tasks yielding reflexive and adaptive responses as well as auditory acuity for both vocal and articulatory features. Results No group differences were found for any measures of auditory-motor control, conflicting with prior findings in PwPD while off medication. Auditory-motor measures were also compared with listener ratings of speech function: first formant frequency acuity was related to speech intelligibility, whereas adaptive responses to vocal fundamental frequency manipulations were related to speech naturalness. Conclusions These results support that auditory-motor processes for both voice and articulatory features are intact for PwPD receiving medication. This work is also the first to suggest associations between measures of auditory-motor control and speech intelligibility and naturalness.

The Decisive Role of Non-Decision Time for Interpreting the Parameters of Decision Making Models

Computational models of decision making are becoming increasingly popular to interpret reaction time and choice data in terms of decision and non-decision related processes. But current evidence remains scarce as to whether parameters of a mathematical model such as the Drift Diffusion Model (DDM) can recover genuine latent psychological processes. In this study, we combine an experimental approach using a decision making task with a physiological decomposition of each reaction time into a motor and pre-motor time using electro-myography. The aim is to test whether the non-decision time parameter of a DDM, assumed to contain encoding and motor processes, varies according to both psychophysical predictions of stimulus encoding and the physiological measurement of motor processes. Our results show that 1) the encoding time is accounted by a DDM only in the case of instructions emphasizing speed over accuracy and 2) that the onset of muscular activity does not sign the end of the accumulation of evidence. This questions the ability of DDM to account for how participants achieve speed-accuracy tradeoff as well as the interpretability of its parameters in terms of decision and non-decision processes.

The Effect of Navigation Demand on Decision Making in a Dynamic, Sport-Inspired Virtual Environment

Athletes commonly make decisions about the passability of closing gaps when navigating sport environments. This study examined whether increased temporal pressure to arrive at a desired location modifies these decisions. Thirty participants navigated toward a waypoint in a virtual, sport-inspired environment. To do so, they had to decide whether they could pass through closing gaps of virtual humans (and take the shortest route) or steer around them (and take a longer route). The decision boundary of participants who were time pressured to arrive at a waypoint was biased toward end gaps of smaller sizes and was less reliably defined, resulting in a higher number of collisions. Effects of temporal pressure were minimized with experience in the experimental task. Results indicate that temporal pressure affects perceptual–motor processes supporting information pickup and shapes the information–action coupling that drives compliance with navigation demands. Theoretical and practical implications are discussed.

Speeding-up while growing-up: Synchronous functional development of motor and non-motor processes across childhood and adolescence

Describing the maturation of information processing in children is fundamental for developmental science. Although non-linear changes in reaction times have been well-documented, direct measurement of the development of the different processing components is lacking. In this study, electromyography was used to quantify the maturation of premotor and motor processes on a sample of 114 children (6–14 years-old) and 15 adults. Using a model-based approach, we show that the development of these two components is well-described by an exponential decrease in duration, with the decay rate being equal for the two components. These findings provide the first unbiased evidence in favour of the common developmental rate of nonmotor and motor processes by directly confronting rates of development of different processing components within the same task. This common developmental rate contrasts with the differential physical maturation of region-specific cerebral gray and white matter. Tentative paths of interpretation are proposed in the discussion.