Bilateral parieto‐frontal network for verbal working memory: an interference approach using repetitive transcranial magnetic stimulation (rTMS)

Abstract

Verbal working memory has been attributed to a left-dominant neuronal network, including parietal, temporal and prefrontal cortical areas. The current study was designed to evaluate the contribution of these brain regions to verbal working memory processes and to assess possible hemispheric asymmetry. The effect of repetitive transcranial stimulation (rTMS) on performance in a verbal working memory task both during, and after an rTMS train (110% of individual motor threshold, 4 Hz) over nine different scalp locations was studied [bilateral middle frontal gyrus (MFG), bilateral supramarginal gyrus (SMG), bilateral inferior parietal cortex (IP) and three different midline control sites]. Significant performance deterioration was observed during rTMS over the left and right MFG and left and right IP. There was no consistent interference effect across subjects over the left or right SMG and the three different midline control sites. The interference effect with the given stimulation parameters did not last beyond the rTMS train itself. The data provide evidence for a symmetrical, bilateral parieto-frontal verbal working memory network. The data are discussed with respect to the competing ideas of a parieto-frontal central executive network vs. a network that processes the inherent semantic and object features of the visually presented verbal stimuli in parallel.

Repetitive Transcranial Magnetic Stimulation Dissociates Working Memory Manipulation from Retention Functions in the Prefrontal, but not Posterior Parietal, Cortex

“…For example, delay-period activity during spatial delayed response (Brandt, Ploner, Meyer, Leistner, & Villringer, 1998;Pascual-Leone & Hallett, 1994) might be sensory, attentional, motoric, or some combination of these. The n-back task (Mottaghy, Gangitano, Krause, & Pascual-Leone, 2003;Mottaghy, Doring, Muller-Gartner, Topper, & Krause, 2002;Mottaghy et al, 2000) requires the simultaneous engagement of several retention-and control-related operations. The absence of laterality effect in our rTMS results is also consistent with the existing literature, which documents disruption of verbal working memory performance with right hemisphere as well as left hemisphere rTMS (e.g., Herwig et al, 2003;Mottaghy et al, 2002).…”

“…The n-back task (Mottaghy, Gangitano, Krause, & Pascual-Leone, 2003;Mottaghy, Doring, Muller-Gartner, Topper, & Krause, 2002;Mottaghy et al, 2000) requires the simultaneous engagement of several retention-and control-related operations. The absence of laterality effect in our rTMS results is also consistent with the existing literature, which documents disruption of verbal working memory performance with right hemisphere as well as left hemisphere rTMS (e.g., Herwig et al, 2003;Mottaghy et al, 2002). This may be because of the complex and distributed nature of the networks that support verbal working memory (e.g., Mottaghy et al, 2002Mottaghy et al, , 2003 and/ or that rTMS of a right hemisphere target is expected to have strong effects on the homologous contralateral region (Ferrarelli et al, 2004;Bestmann, Baudewig, Siebner, Rothwell, & Frahm, 2003).…”

The Inferior Frontal Gyrus and Phonological Processing: An Investigation using rTMS

“…In a more complex design it would be possible to compare the effects of stimulating at different times during the delay, but increasing the duration of the pulse train at the frequency used here would not be possible without exceeding current safety guidelines ( Wassermann, 1998). Mottaghy et al (2002) applied TMS constantly at 4 Hz during the 30-sec performance block of a 2-back verbal WM task. As in the present study accuracy, but not RT, was the principal indicator of behavioral impairment related to prefrontal stimulation.…”

“…Studies of frontal lobe language functions have remained largely restricted to frontal regions outside Broca's area; these have demonstrated that TMS can be used to disrupt verbal working memory (WM) (Mottaghy et al, 2000;Mottaghy, Doring, Muller-Gartner, Topper, & Krause, 2002) and verb generation (Shapiro, Pascual-Leone, Mottaghy, Gangitano, & Caramazza, 2001). TMS studies attempting to reproduce some of the production deficits associated with Broca's aphasia have had limited success (Stewart, Walsh, Frith, & Rothwell, 2001;Flitman et al, 1998;Epstein et al, 1996Epstein et al, , 1999.…”

Preceding attention and the dorsomedial prefrontal cortex: Process specificity versus domain dependence

“…Goldman-Rakic and others Goldman-Rakic, 2000;Levy and Goldman-Rakic, 2000;Mottaghy et al, 2002;Ungerleider et al, 1998] argue for what they call domain-specificity. Domain specificity reflects functional organization with regard to a certain class of stimuli or content, i.e., the domain (such as verbal or spatial in the case of working memory) independently of the required task or process.…”