Blog Archives

Literal, fictive and metaphorical motion sentences preserve the motion component of the verb: A TMS study

We used Transcranial Magnetic Stimulation (TMS) to assess whether reading literal, non-literal (i.e., metaphorical, idiomatic) and fictive motion sentences modulates the activity of the motor system. Sentences were divided into three segments visually presented one at a time: the noun phrase, the verb and the final part of the sentence. Single pulse-TMS was delivered at the end of the sentence over the leg motor area in the left hemisphere and motor evoked potentials (MEPs) were recorded from the right gastrocnemius and tibialis anterior muscles. MEPs were larger when participants were presented with literal, fictive and metaphorical motion sentences than with idiomatic motion or mental sentences. These results suggest that the excitability of the motor system is modulated by the motor component of the verb, which is preserved in fictive and metaphorical motion sentences.

from Brain and Language

Modulation of the motor system during visual and auditory language processing

Studies of embodied cognition have demonstrated the engagement of the motor system when people process action-related words and concepts. However, research using transcranial magnetic stimulation (TMS) to examine linguistic modulation in primary motor cortex has produced inconsistent results. Some studies report that action words produce an increase in corticospinal excitability; others, a decrease. Given the differences in methodology and modality, we re-examined this issue, comparing conditions in which participants either read or listened to the same set of action words. In separate blocks of trials, participants were presented with lists of words in the visual and auditory modality, and a TMS pulse was applied over left motor cortex, either 150 or 300 ms after the word onset. Motor evoked potentials (MEPs) elicited were larger following the presentation of action words compared with control words. However, this effect was only observed when the words were presented visually; no changes in MEPs were found when the words were presented auditorily. A review of the TMS literature on action word processing reveals a similar modality effect on corticospinal excitability. We discuss different hypotheses that might account for this differential modulation of action semantics by vision and audition.

from Experimental Brain Research

Vocal pitch discrimination in the motor system

Speech production can be broadly separated into two distinct components: Phonation and Articulation. These two aspects require the efficient control of several phono-articulatory effectors. Speech is indeed generated by the vibration of the vocal-folds in the larynx (F0) followed by ‘‘filtering” by articulators, to select certain resonant frequencies out of that wave (F1, F2, F3, etc.). Recently it has been demonstrated that the motor representation of articulators (lips and tongue) participates in the discrimination of articulatory sounds (lips- and tongue-related speech sounds). Here we investigate whether the results obtained on articulatory sounds discrimination could be extended to phonation by applying a dual-pulse TMS protocol while subjects had to discriminate F0-shifted vocal utterances [a]. Stimulation over the larynx motor representation, compared to the control site (tongue/lips motor cortex), induced a reduction in RT for stimuli including a subtle pitch shift. We demonstrate that vocal pitch discrimination, in analogy with the articulatory component, requires the contribution of the motor system and that this effect is somatotopically organized.

from Brain and Language

Contribution of frontal cortex to the spatial representation of number

Neuropsychological and neurophysiological studies have suggested that prefrontal cortex may be involved in non-verbal number processing, when relevant for current behavioural goals. More precisely, it has been suggested that an intact right inferior frontal gyrus (rIFG) in humans may be necessary to the use of a spatial representation of numbers, also known as mental number line. In a popular model of spatial functions (e.g., Corbetta et al., 2008), rIFG is part of a right-lateralised ventral fronto-parietal network that conveys signals to a dorsal network supporting attentional orienting in contralateral space. Within the dorsal network, the frontal eye fields (FEF) are known to contribute to visual scene analysis and visual conjunction search tasks when eye movement commands are not required. In the present study, we hypothesised they might also be involved in exploring a conceptual space, such as the mental number line. We examined the proposed functions of the human rIFG and right Frontal Eye Field (rFEF) by interfering with their normal functioning with repetitive Transcranial Magnetic Stimulation (rTMS) while participants performed numerical tasks. The results suggest that, when number magnitude is relevant to the task, rIFG supports orienting to the entire mental number line while rFEF are crucial for contralateral orienting (that is towards small numbers).

from Cortex

A case for the involvement of phonological loop in sentence comprehension

We suggest that the neural correlates of the phonological loop, left BA40 and BA44, are both involved in the comprehension of syntactically complex sentences, while only left BA40, corresponding to the short-term store, is recruited for the comprehension of long but syntactically simple sentences. Therefore, in contrast with the dominant view, we showed that sentence comprehension is a function of the phonological loop.

from Neuropsychologia

Burst transcranial magnetic stimulation: which tinnitus characteristics influence the amount of transient tinnitus suppression?

Burst TMS modulates both unilateral and bilateral tinnitus, both high and low distress and both pure tones and narrow band tinnitus. However, the suppression effect is moderated by tinnitus type and laterality, tinnitus-related distress, and tinnitus duration.

from the European Journal of Neurology

Stimulating conversation: Enhancement of elicited propositional speech in a patient with chronic non-fluent aphasia following transcranial magnetic stimulation

Although evidence suggests that patients with left hemisphere strokes and non-fluent aphasia who receive 1 Hz repetitive transcranial magnetic stimulation (rTMS) over the intact right inferior frontal gyrus experience persistent benefits in naming, it remains unclear whether the effects of rTMS in these patients generalize to other language abilities. We report a subject with chronic non-fluent aphasia who showed stable deficits of elicited propositional speech over the course of 5 years, and received 1200 pulses of 1 Hz rTMS daily for 10 days at a site identified as being optimally responsive to rTMS in this patient. Consistent with prior studies there was improvement in object naming, with a statistically significant improvement in action naming. Improvement was also demonstrated in picture description at 2, 6, and 10 months after rTMS with respect to the number of narrative words and nouns, sentence length, and use of closed class words. Compared to his baseline performance, the patient showed significant improvement on the Western Aphasia Battery (WAB) subscale for spontaneous speech. These findings suggest that manipulation of the intact contralesional cortex in patients with non-fluent aphasia may result in language benefits that generalize beyond naming to include other aspects of language production.

from Brain and Language