Michael A Arbib

We assess the challenges of studying action and language mechanisms in the brain, both singly and in relation to each other to provide a novel perspective on neuroinformatics, integrating the development of databases for encoding – separately or together – neurocomputational models and empirical data that serve systems and cognitive neuroscience.

Winner-take-all models are commonly used to model decision-making tasks where one outcome must be selected from several competing options. Related random walk and diffusion models have been used to explain such processes and apply them to psychometric and neurophysiological data. Recent model-based fMRI studies have sought to find the neural correlates of decision-making processes. However, due to the fact that hemodynamic responses likely reflect synaptic rather than spiking activity, the expected BOLD signature of winner-take-all circuits is not clear. A powerful way to integrate data from neurophysiology and brain imaging is by developing biologically plausible neural network models constrained and testable by neural and behavioral data, and then using Synthetic Brain Imaging - transforming the output of simulations with the model to make predictions testable against neuroimaging data. We developed a biologically realistic spiking winner-take-all model comprised of coupled excitatory and inhibitory neural populations. We varied the difficulty of a decision-making task by adjusting the contrast, or relative strength of inputs representing two response options. Synthetic brain imaging was used to estimate the BOLD response of the model and analyze its peak as a function of input contrast. We performed a parameter space analysis to determine values for which the model performs the task accurately, and given accurate performance, the distribution of the input contrast-BOLD response relationship. This underscores the need for models grounded in neurophysiological data for brain imaging analyses which attempt to localize the neural correlates of cognitive processes based on predicted BOLD responses.

The paper introduces mirror neuron system II (MNS2), a new version of the MNS model (Oztop and Arbib in Biol Cybern 87 (2):116-140, 2002) of action recognition learning by mirror neurons of the macaque brain. The new model uses a recurrent architecture that is biologically more plausible than that of the original model. Moreover, MNS2 extends the capacity of the model to address data on audio-visual mirror neurons and on the response of mirror neurons when the target object was recently visible but is currently hidden.

Optic flow is the vector field induced on the retina by the movement of features in the external world. We address the stimulus-matching problem of approximating the optic flow with a velocity vector field inferred from hypothesized matching of features in successive “retinal ...

... With Stage 6, we have defined a highly socialized hominid with a variety of more or less conventionalized manual, orofacial, and vocal gestures which refer to something else—we have come a long way from the original mirror system for grasping in which a hand movement ...

... Theories of abstract automata. Post a Comment. CONTRIBUTORS: Author: Arbib, Michael A. PUBLISHER: ... PUB ID: 101-339-501 (Last edited on 2002/02/27 17:13:26 US/Mountain). SPONSOR(S): ABSTRACT: Bibliography: p. 389-400. STATISTICS. Click on # to view. Citations, ...

A patient with schizophrenia may generate an action (whether manual or verbal), but not attribute the generation of that action to himself. We distinguish self-monitoring and attribution of agency, relating only the former to forward models and the mirror system. We suggest that alien hand experiences occur when an action progresses through hand control pathways with no record of disinhibition having been kept and is then seen but dismissed as external. Analogously, auditory pathways are active during verbal hallucinations and produce a subvocal verbal process, but since no record is kept of the words being created, they are treated as external. The subject then proceeds to confabulate, to provide an account for the agency.

Positron emission tomography (PET) brain mapping was used to investigate whether or not human dorsal premotor cortex is involved in selecting motor acts based on arbitrary visual stimuli. Normal subjects performed four movement selection tasks. A manipulandum with three graspable stations was used. An imperative visual cue (LEDs illuminated in random order) indicated which station to grasp next with no instructional delay period. In a power task, a large aperture power grip was used for all trials, irrespective of the LED color. In a precision task, a pincer grasp of thumb and index finger was used. In a conditional task, the type of grasp (power or precision) was randomly determined by LED color. Comparison of the conditional selection task versus the average of the power and precision tasks revealed increased blood flow in left dorsal premotor cortex and superior parietal lobule. The average rate of producing the different grasp types and transport to the manipulandum stations was...

... Edition, edited by Stuart Shapiro, 2:1427-1443, Wiley. Bischoff-Grethe, A., Spoelstra, J. & Arbib, MA (2001) Brain Models on the Web and the Need for Summary Data. ... Scholarpedia, 2(12):3487. Philip Holmes and Eric T. Shea-Brown (2006) Stability. Scholarpedia, 1(10):1838. ...