Left Posterior Middle Frontal Gyrus Research Articles

Secondary motor areas for response inhibition: an epicortical recording and stimulation study.

The areas that directly inhibit motor responses in the human brain remain not fully clarified, although the pre-supplementary motor area and lateral premotor areas have been implicated. The objective of the present study was to delineate the critical areas for response inhibition and the associated functional organization of the executive action control system in the frontal lobe. The subjects were eight intractable focal epilepsy patients with chronic subdural or depth electrode implantation for presurgical evaluation covering the frontal lobe (five for left hemisphere, three for right). We recorded event-related potentials to a Go/No-Go task. We then applied a brief 50 Hz electrical stimulation to investigate the effect of the intervention on the task. Brief stimulation was given to the cortical areas generating discrete event-related potentials specific for the No-Go trials (1–3 stimulation sites/patient, a total of 12 stimulation sites). We compared the locations of event-related potentials with the results of electrical cortical stimulation for clinical mapping. We also compared the behavioural changes induced by another brief stimulation with electrical cortical stimulation mapping. As the results, anatomically, No-Go-specific event-related potentials with relatively high amplitude, named ‘large No-Go event-related potentials’, were observed predominantly in the secondary motor areas, made up of the supplementary motor area proper, the pre-supplementary motor area, and the lateral premotor areas. Functionally, large No-Go event-related potentials in the frontal lobe were located at or around the negative motor areas or language-related areas. Brief stimulation prolonged Go reaction time at most stimulation sites (66.7%) [P < 0.0001, effect size (d) = 0.30, Wilcoxon rank sum test], and increased No-Go error at some stimulation sites (25.0%: left posterior middle frontal gyrus and left pre-supplementary motor area). The stimulation sites we adopted for brief stimulation were most frequently labelled ‘negative motor area’ (63.6%), followed by ‘language-related area’ (18.2%) by the electrical cortical stimulation mapping. The stimulation sites where the brief stimulation increased No-Go errors tended to be labelled ‘language-related area’ more frequently than ‘negative motor area’ [P = 0.0833, Fisher’s exact test (two-sided)] and were located more anteriorly than were those without a No-Go error increase. By integrating the methods of different modality, namely, event-related potentials combined with brief stimulation and clinical electrical cortical stimulation mapping, we conducted a novel neuroscientific approach, providing direct evidence that secondary motor areas, especially the pre-supplementary motor area and posterior middle frontal gyrus, play an important role in response inhibition.

Auditory Attention following a Left Hemisphere Stroke: Comparisons of Alerting, Orienting, and Executive Control Performance Using an Auditory Attention Network Test

ABSTRACT Auditory attention is a critical foundation for successful language comprehension, yet is rarely studied in individuals with acquired language disorders. We used an auditory version of the well-studied Attention Network Test to study alerting, orienting, and executive control in 28 persons with chronic stroke (PWS). We further sought to characterize the neurobiology of each auditory attention measure in our sample using exploratory lesion-symptom mapping analyses. PWS exhibited the expected executive control effect (i.e., decreased accuracy for incongruent compared to congruent trials), but their alerting and orienting attention were disrupted. PWS did not exhibit an alerting effect and they were actually distracted by the auditory spatial orienting cue compared to the control cue. Lesion-symptom mapping indicated that poorer alerting and orienting were associated with damage to the left retrolenticular part of the internal capsule (adjacent to the thalamus) and left posterior middle frontal gyrus (overlapping with the frontal eye fields), respectively. The behavioral findings correspond to our previous work investigating alerting and spatial orienting attention in persons with aphasia in the visual modality and suggest that auditory alerting and spatial orienting attention may be impaired in PWS due to stroke lesions damaging multi-modal attention resources.

Men and women differ in the neural basis of handwriting.

There is an ongoing debate about whether, and to what extent, males differ from females in their language skills. In the case of handwriting, a composite language skill involving language and motor processes, behavioral observations consistently show robust sex differences but the mechanisms underlying the effect are unclear. Using functional magnetic resonance imaging (fMRI) in a copying task, the present study examined the neural basis of sex differences in handwriting in 53 healthy adults (ages 19–28, 27 males). Compared to females, males showed increased activation in the left posterior middle frontal gyrus (Exner's area), a region thought to support the conversion between orthographic and graphomotor codes. Functional connectivity between Exner's area and the right cerebellum was greater in males than in females. Furthermore, sex differences in brain activity related to handwriting were independent of language material. This study identifies a novel neural signature of sex differences in a hallmark of human behavior, and highlights the importance of considering sex as a factor in scientific research and clinical applications involving handwriting.

The Relationship between Intrinsic Couplings of the Visual Word Form Area with Spoken Language Network and Reading Ability in Children and Adults

Reading plays a key role in education and communication in modern society. Learning to read establishes the connections between the visual word form area (VWFA) and language areas responsible for speech processing. Using resting-state functional connectivity (RSFC) and Granger Causality Analysis (GCA) methods, the current developmental study aimed to identify the difference in the relationship between the connections of VWFA-language areas and reading performance in both adults and children. The results showed that: (1) the spontaneous connectivity between VWFA and the spoken language areas, i.e., the left inferior frontal gyrus/supramarginal gyrus (LIFG/LSMG), was stronger in adults compared with children; (2) the spontaneous functional patterns of connectivity between VWFA and language network were negatively correlated with reading ability in adults but not in children; (3) the causal influence from LIFG to VWFA was negatively correlated with reading ability only in adults but not in children; (4) the RSFCs between left posterior middle frontal gyrus (LpMFG) and VWFA/LIFG were positively correlated with reading ability in both adults and children; and (5) the causal influence from LIFG to LSMG was positively correlated with reading ability in both groups. These findings provide insights into the relationship between VWFA and the language network for reading, and the role of the unique features of Chinese in the neural circuits of reading.

Spontaneous gesture and spatial language: Evidence from focal brain injury

People often use spontaneous gestures when communicating spatial information. We investigated focal brain-injured individuals to test the hypotheses that (1) naming motion event components of manner-path (represented by verbs–prepositions in English) are impaired selectively, (2) gestures compensate for impaired naming. Patients with left or right hemisphere damage (LHD or RHD) and elderly control participants were asked to describe motion events (e.g., running across) depicted in brief videos. Damage to the left posterior middle frontal gyrus, left inferior frontal gyrus, and left anterior superior temporal gyrus (aSTG) produced impairments in naming paths of motion; lesions to the left caudate and adjacent white matter produced impairments in naming manners of motion. While the frequency of spontaneous gestures were low, lesions to the left aSTG significantly correlated with greater production of path gestures. These suggest that producing prepositions–verbs can be separately impaired and gesture production compensates for naming impairments when damage involves left aSTG.

Automatic domain-general processing of sound source identity in the left posterior middle frontal gyrus

Identifying sound sources is fundamental to developing a stable representation of the environment in the face of variable auditory information. The cortical processes underlying this ability have received little attention. In two fMRI experiments, we investigated passive adaptation to (Exp. 1) and explicit discrimination of (Exp. 2) source identities for different categories of auditory objects (voices, musical instruments, environmental sounds). All cortical effects of source identity were independent of high-level category information, and were accounted for by sound-to-sound differences in low-level structure (e.g., loudness). A conjunction analysis revealed that the left posterior middle frontal gyrus (pMFG) adapted to identity repetitions during both passive listening and active discrimination tasks. These results indicate that the comparison of sound source identities in a stream of auditory stimulation recruits the pMFG in a domain-general way, i.e., independent of the sound category, based on information contained in the low-level acoustical structure. pMFG recruitment during both passive listening and explicit identity comparison tasks also suggests its automatic engagement in sound source identity processing.

Naming and gesturing spatial relations: Evidence from focal brain-injured individuals

Spatial language helps us to encode relations between objects and organize our thinking. Little is known about the neural instantiations of spatial language. Using voxel-lesion symptom mapping (VLSM), we tested the hypothesis that focal brain injured patients who had damage to left frontal–parietal peri-Sylvian regions would have difficulty in naming spatial relations between objects. We also investigated the relationship between impaired verbalization of spatial relations and spontaneous gesture production. Patients with left or right hemisphere damage and elderly control participants were asked to name static (e.g., an apple on a book) and dynamic (e.g., a pen moves over a box) locative relations depicted in brief video clips. The correct use of prepositions in each task and gestures that represent the spatial relations were coded. Damage to the left posterior middle frontal gyrus, the left inferior frontal gyrus, and the left anterior superior temporal gyrus were related to impairment in naming spatial relations. Production of spatial gestures negatively correlated with naming accuracy, suggesting that gestures might help or compensate for difficulty with lexical access. Additional analyses suggested that left hemisphere patients who had damage to the left posterior middle frontal gyrus and the left inferior frontal gyrus gestured less than expected, if gestures are used to compensate for impairments in retrieving prepositions.

The effect of long-term high frequency repetitive transcranial magnetic stimulation on working memory in schizophrenia and healthy controls—A randomized placebo-controlled, double-blind fMRI study

In schizophrenia patients negative symptoms and cognitive impairment often persist despite treatment with second generation antipsychotics leading to reduced quality of life and psychosocial functioning. One core cognitive deficit is impaired working memory (WM) suggesting malfunctioning of the dorsolateral prefrontal cortex. High frequency repetitive transcranial magnetic stimulation (rTMS) has been used to transiently facilitate or consolidate neuronal processes. Pilot studies using rTMS have demonstrated improvement of psychopathology in other psychiatric disorders, but a systematic investigation of working memory effects outlasting the stimulation procedure has not been performed so far. The aim of our study was to explore the effect of a 3-week high frequency active or sham 10Hz rTMS on cognition, specifically on working memory, in schizophrenia patients (n=25) in addition to antipsychotic therapy and in healthy controls (n=22). We used functional magnetic resonance imaging (fMRI) to compare activation patterns during verbal WM (letter 2-back task) before and after 3-weeks treatment with rTMS. Additionally, other cognitive tasks were conducted. 10Hz rTMS was applied over the left posterior middle frontal gyrus (EEG electrode location F3) with an intensity of 110% of the individual resting motor threshold (RMT) over a total of 15 sessions. Participants recruited the common fronto- parietal and subcortical WM network. Multiple regression analyses revealed no significant activation differences over time in any contrast or sample. According to the ANOVAs for repeated measures performance remained without alterations in all groups. This is the first fMRI study that has systematically investigated this topic within a randomized, placebo-controlled, double-blind design, contrasting the effects in schizophrenia patients and healthy controls.

Neural substrates for processing task‐irrelevant emotional distracters in maltreated adolescents with depressive disorders: A pilot study

In this pilot study, neural systems related to cognitive and emotional processing were examined using event-related functional magnetic resonance imaging in 5 maltreated youth with depressive disorders and 11 nonmaltreated healthy participants. Subjects underwent an emotional oddball task, where they detected infrequent ovals (targets) within a continual stream of phase-scrambled images (standards). Sad and neutral images were intermittently presented as task-irrelevant distracters. The maltreated youth revealed significantly decreased activation in the left middle frontal gyrus and right precentral gyrus to target stimuli and significantly increased activation to sad stimuli in bilateral amygdala, left subgenual cingulate, left inferior frontal gyrus, and right middle temporal cortex compared to nonmaltreated subjects. Additionally, the maltreated youth showed significantly decreased activation to both attentional targets and sad distracters in the left posterior middle frontal gyrus compared to nonmaltreated subjects. In this exploratory study of dorsal control and ventral emotional circuits, we found that maltreated youth with distress disorders demonstrated dysfunction of neural systems related to cognitive control and emotional processing.

Transcranial Magnetic Stimulation Intensities in Cognitive Paradigms

BackgroundTranscranial magnetic stimulation (TMS) has become an important experimental tool for exploring the brain's functional anatomy. As TMS interferes with neural activity, the hypothetical function of the stimulated area can thus be tested. One unresolved methodological issue in TMS experiments is the question of how to adequately calibrate stimulation intensities. The motor threshold (MT) is often taken as a reference for individually adapted stimulation intensities in TMS experiments, even if they do not involve the motor system. The aim of the present study was to evaluate whether it is reasonable to adjust stimulation intensities in each subject to the individual MT if prefrontal regions are stimulated prior to the performance of a cognitive paradigm.Methods and FindingsRepetitive TMS (rTMS) was applied prior to a working memory task, either at the ‘fixed’ intensity of 40% maximum stimulator output (MSO), or individually adapted at 90% of the subject's MT. Stimulation was applied to a target region in the left posterior middle frontal gyrus (pMFG), as indicated by a functional magnetic resonance imaging (fMRI) localizer acquired beforehand, or to a control site (vertex). Results show that MT predicted the effect size after stimulating subjects with the fixed intensity (i.e., subjects with a low MT showed a greater behavioral effect). Nevertheless, the individual adaptation of intensities did not lead to stable effects.ConclusionTherefore, we suggest assessing MT and account for it as a measure for general cortical TMS susceptibility, even if TMS is applied outside the motor domain.

Localization of sublexical speech perception components

Models of speech perception are in general agreement with respect to the major cortical regions involved, but lack precision with regard to localization and lateralization of processing units. To refine these models we conducted two Activation Likelihood Estimation (ALE) meta-analyses of the neuroimaging literature on sublexical speech perception. Based on foci reported in 23 fMRI experiments, we identified significant activation likelihoods in left and right superior temporal cortex and the left posterior middle frontal gyrus. Sub-analyses examining phonetic and phonological processes revealed only left mid-posterior superior temporal sulcus activation likelihood. A lateralization analysis demonstrated temporal lobe left lateralization in terms of magnitude, extent, and consistency of activity. Experiments requiring explicit attention to phonology drove this lateralization. An ALE analysis of eight fMRI studies on categorical phoneme perception revealed significant activation likelihood in the left supramarginal gyrus and angular gyrus. These results are consistent with a speech processing network in which the bilateral superior temporal cortices perform acoustic analysis of speech and non-speech auditory stimuli, the left mid-posterior superior temporal sulcus performs phonetic and phonological analysis, and the left inferior parietal lobule is involved in detection of differences between phoneme categories. These results modify current speech perception models in three ways: (1) specifying the most likely locations of dorsal stream processing units, (2) clarifying that phonetic and phonological superior temporal sulcus processing is left lateralized and localized to the mid-posterior portion, and (3) suggesting that both the supramarginal gyrus and angular gyrus may be involved in phoneme discrimination.

Stronger inference with direct manipulation of brain function

At an early stage in our educations we have all learned that statistical significance need not imply functional significance, and, relatedly, that correlation does not imply causation. Despite these caveats, it is indisputable that cognitive neuroscience has learned a great deal about the neural bases of behaviour via the fundamentally correlative methods of functional neuroimaging. This is particularly true in cases when a carefully controlled neuroimaging study can illustrate functional properties of a brain region whose necessity for a particular aspect of behaviour has been established with lesion data. There can arise, however, situations in which two different neuroimaging studies (and indeed, as we will review here, two different analyses of the same data set) produce mutually incompatible results, thereby leaving ambiguous the nature of the structure-function mapping that the experiments were designed to address. This is a situation in which the ability to locally alter brain function in a prospective manner can be particularly useful. The aspect of cognition that is at issue in this commentary is the short-term retention (STR, a.k.a. “storage” or “maintenance”) of information that is required by tests of short-term and working memory. One way to operationalise this construct is to vary the number of items that must be retained on different trials. Prompted by a review of studies that manipulated verbal memory load in this way, we applied two different analyses to the data from a sample of 24 subjects retaining 2 vs. 5 letters in a (7 sec) delayed-recognition task during functional magnetic resonance imaging (fMRI): a spatially normalized group-average (SNGA) analysis; and singlesubject (SS) analyses that treated each subject’s data as an individual case (Feredoes and Postle, 2007). The SNGA analysis revealed a region in left posterior middle frontal gyrus (MFG) of the prefrontal cortex (PFC), near the border of Brodmann Areas 9 and 6, that was reliably sensitive to the manipulation of load, and, therefore, a candidate locus for the STR of verbal information. (This also replicated the findings of previous studies that had also used SNGA analyses (e.g., Narayanan et al., 2005).) The SS analyses, in contrast, produced results that were topographically highly variable across subjects and, notably, did not include the left posterior MFG in any subject. Instead, the regions demonstrating load effects were best summarized as occurring in left posterior perisylvian cortex in the majority of subjects. These results prompted us to address the obvious question of which brain regions, those identified by the SNGA or the SS analyses, contributed more importantly to the STR of information in our task? (Although it was empirically plausible that the two sets of regions could make functionally comparable contributions, the two sets of results were difficult to reconcile theoretically (Postle, 2006).) To address this question, we performed a second study that would

Correlations between measures of executive attention and cortical thickness of left posterior middle frontal gyrus - a dichotic listening study.

BackgroundThe frontal lobe has been associated to a wide range of cognitive control functions and is also vulnerable to degeneration in old age. A recent study by Thomsen and colleagues showed a difference between a young and old sample in grey matter density and activation in the left middle frontal cortex (MFC) and performance on a dichotic listening task. The present study investigated this brain behaviour association within a sample of healthy older individuals, and predicted a positive correlation between performance in a condition requiring executive attention and measures of grey matter structure of the posterior left MFC.MethodsA dichotic listening forced attention paradigm was used to measure attention control functions. Subjects were instructed to report only the left or the right ear syllable of a dichotically presented consonant-vowel syllable pair. A conflict situation appears when subjects are instructed to report the left ear stimulus, caused by the conflict with the bottom-up, stimulus-driven right ear advantage. Overcoming this processing conflict was used as a measure of executive attention. Thickness and volumes of frontal lobe regions were derived from automated segmentation of 3D magnetic resonance image acquisitions.ResultsThe results revealed a statistically significant positive correlation between the thickness measure of the left posterior MFC and performance on the dichotic listening measures of executive attention. Follow-up analyses showed that this correlation was only statistically significant in the subgroup that showed the typical bottom-up, stimulus-driven right ear advantage.ConclusionThe results suggest that the left MFC is a part of an executive attention network, and that the dichotic listening forced attention paradigm may be a feasible tool for assessing subtle attentional dysfunctions in older adults.

Further Dissociating the Processes Involved in Recognition Memory: An fMRI Study

Based on an event-related potential study by Rugg et al. [Dissociation of the neural correlates of implicit and explicit memory. Nature, 392, 595-598, 1998], we attempted to isolate the hemodynamic correlates of recollection, familiarity, and implicit memory within a single verbal recognition memory task using event-related fMRI. Words were randomly cued for either deep or shallow processing, and then intermixed with new words for yes/no recognition. The number of studied words was such that, whereas most were recognized ("hits"), an appreciable number of shallow-studied words were not ("misses"). Comparison of deep hits versus shallow hits at test revealed activations in regions including the left inferior parietal gyrus. Comparison of shallow hits versus shallow misses revealed activations in regions including the bilateral intraparietal sulci, the left posterior middle frontal gyrus, and the left frontopolar cortex. Comparison of hits versus correct rejections revealed a relative deactivation in an anterior left medial-temporal region (most likely the perirhinal cortex). Comparison of shallow misses versus correct rejections did not reveal response decreases in any regions expected on the basis of previous imaging studies of priming. Given these and previous data, we associate the left inferior parietal activation with recollection, the left anterior medial-temporal deactivation with familiarity, and the intraparietal and prefrontal responses with target detection. The absence of differences between shallow misses and correct rejections means that the hemodynamic correlates of implicit memory remain unclear.

Covert reorienting and inhibition of return: an event-related fMRI study.

Using event-related fMRI, we analyzed the functional neuroanatomy of covert reorienting and inhibition of return (IOR). Covert reorienting to a target appearing within 250 msec after an invalid contralateral location cue elicited increased activation in the left fronto-polar cortex (LFPC), right anterior and left posterior middle frontal gyrus, and right cerebellum, areas that have previously been associated with attentional processes, specifically attentional change. In contrast, IOR, which leads to prolonged response times to targets that appear at the cued location at a stimulus-onset-asynchrony (SOA)>250 msec, was accompanied by increased activation in brain areas involved in oculomotor programming, such as the right medial frontal gyrus (supplementary eye field; SEF) and the right inferior precentral sulcus (frontal eye field; FEF), supporting the oculomotor bias theory of IOR. Pre-SEF and pre-FEF areas were involved both in covert reorienting and IOR. The supramarginal gyri were bilaterally involved in IOR, with the right supramarginal gyrus additionally involved in covert reorienting.

Effects of incidental and intentional feature binding on recognition: a behavioural and PET activation study

Using Positron Emission Tomography (PET), we investigated cerebral regions associated with the episodic recognition of words alone and words bound to contextual colours. Two modes of colour encoding were tested: incidental and intentional word-to-colour binding. Word-only recognition was associated with brain activation in a lexico-semantic left middle temporal region and in the cerebellum following an incidental colour encoding, and with brain activation in the left posterior middle frontal gyrus, right anterior cingulate and right inferior frontal gyrus following an intentional encoding. Recognition of bound features was associated with activation in left prefrontal and superior parietal regions following an incidental colour encoding, and with preferential right prefrontal cortex activation following an intentional colour encoding. Our results are in line with the hypothesis of a parietal involvement in context processing, and prefrontal areas in monitoring retrieval processes. Our results also support the hypothesis of a ‘cortical asymmetry for reflective activity’ (CARA).