Ventral and dorsal fiber systems for imagined and executed movement

Abstract

Although motor imagery is an entirely cognitive process, it shows remarkable similarity to overt movement in behavioral and physiological studies. In concordance, brain imaging studies reported shared fronto-parietal sensorimotor networks commonly engaged by both tasks. However, differences in prefrontal and parietal regions point toward additional cognitive mechanisms in the context of imagery. Within the perspective of a general dichotomization into dorsal and ventral processing streams in the brain, the question arises whether motor imagery and overt movement could differentially involve the dorsal or ventral system. Therefore, we combined fMRI and DTI data of 20 healthy subjects to analyze the anatomical characteristics of connecting fronto-parietal association pathways of imagined and overt movements. We found a dichotomy of fiber pathways into dorsal and ventral systems: the superior longitudinal fascicle (SLF II-III) was found to connect frontal and parietal regions involved in both overt and imagined movements, whereas a ventral tract via the extreme/external capsule (EmC/EC) connects cortical regions specific for motor imagery that were situated more anteriorly and posteriorly. We suppose that motor imagery-related kinesthetic emulations are embedded into dorsal sensorimotor networks, and imagery-specific cognitive functions are implemented in the ventral system. These findings have implications for models of motor cognition.

Bottom-Up and Top-Down Visuomotor Responses to Action Observation

“…The present interpretation of the data by no means excludes the possibility of a cross-talk between bottom-up and top-down processes, which are known to influence each other at several levels of response processing. This datum actually fits well with models proposed in nonhuman primates (Boussaoud et al 1995;Lebedev and Wise 2002) and in humans Toni, Rushworth, et al 2001;Vry et al 2012) describing 2 routes to action that rely on the dorsal and the ventral visual streams. An additional dissociated effect of rTMS over the 2 target areas is that parietal stimulation produced an effect on the representation of the congruent movement, that is, on the movement that was seen in the visual stimulus and, on the contrary, prefrontal stimulation produced an effect limited to the incongruent movement, that is, to the movement that was NOT seen in the visual stimulus but that had to be implemented in the countermirror task.…”

Variable motor imagery training induces sleep memory consolidation and transfer improvements

“…So far, there are several data supporting that MI and physical practice share the same neural substrate, although there are also some differences within the pattern of activity in these areas (Hetu et al, 2013). Notably, Lacourse, Turner, Randolph-Orr, Schandler, and Cohen (2004) reported that MI training was accompanied by an increased activation of M1, but to a lesser extent compared to physical practice, while Vry et al (2012) found that the DLPFC and the parietal cortex are anatomically connected and more activated during MI than actual execution. Based on these findings, we may hypothesize that during constant MI practice, M1 activation might be less important than that of the DLPFC during variable practice, and this ''unbalancedactivation'' could, therefore, be effective in the motor output following a consolidation period that includes a night of sleep.…”

The Neurobiological Grounding of Persistent Stuttering: from Structure to Function

“…From this, it follows that the interhemispheric transmission is fastest and most efficient in this area which is capable of transmitting reliable, precisely timed neuronal coupling. Hence, it is plausible that the frequency-specific interhemispheric correlation structure of spontaneous oscillatory neuronal activity is nested in the highest frequency range (32)(33)(34)(35)(36)(37)(38)(39)(40)(41)(42)(43)(44)(45) between the sensorimotor cortices compared to the temporal lobes (4-6 Hz) and the lateral parietal areas (8-23 Hz) [58]. Large-diameter axon fibers may also determine the degree of interhemisphericcorrelated fMRI resting-state activity which is again highest in the somatosensory cortices [59].…”

“…The key to fluent speech is a production-perception interaction. The timely sequencing and context-dependent binding of speech units are constantly monitored and adjusted by an effective sensorimotor integration [39]. Feedback-related control couples not only perception and production processes but also internal models that closely relate to the sound envelop of a corresponding utterance [40] possibly translating auditory targets into motor commands.…”