Neural correlates of the processing of co-speech gestures

In communicative situations, speech is often accompanied by gestures. For example, speakers tend to illustrate certain contents of speech by means of iconic gestures which are hand movements that bear a formal relationship to the contents of speech. The meaning of an iconic gesture is determined both by its form as well as the speech context in which it is performed. Thus, gesture and speech interact in comprehension. Using fMRI, the present study investigated what brain areas are involved in this interaction process. Participants watched videos in which sentences containing an ambiguous word (e.g. She touched the mouse) were accompanied by either a meaningless grooming movement, a gesture supporting the more frequent dominant meaning (e.g. animal) or a gesture supporting the less frequent subordinate meaning (e.g. computer device). We hypothesized that brain areas involved in the interaction of gesture and speech would show greater activation to gesture-supported sentences as compared to sentences accompanied by a meaningless grooming movement. The main results are that when contrasted with grooming, both types of gestures (dominant and subordinate) activated an array of brain regions consisting of the left posterior superior temporal sulcus (STS), the inferior parietal lobule bilaterally and the ventral precentral sulcus bilaterally. Given the crucial role of the STS in audiovisual integration processes, this activation might reflect the interaction between the meaning of gesture and the ambiguous sentence. The activations in inferior frontal and inferior parietal regions may reflect a mechanism of determining the goal of co-speech hand movements through an observation-execution matching process.     

Neural correlates of woman face processing by 2-month-old infants.

The age of 2 months marks a turn in the development of face processing in humans with the emergence of recognition based on internal feature configuration. We studied the neural bases of this early cognitive expertise, critical for adaptive behavior in the social world, by mapping with positron emission tomography the brain activity of 2-month-old alert infants while looking at unknown woman faces. We observed the activation of a distributed network of cortical areas that largely overlapped the adult face-processing network, including the so-called fusiform face area. We also evidenced the activation of left superior temporal and inferior frontal gyri, regions associated, in adults, with language processing. These findings demonstrates that cognitive development proceeds early in functionally active interconnected cortical areas despite the fact they have not all yet reached full metabolic maturation.     

Neural correlates of relational and item-specific encoding during working and long-term memory in schizophrenia

Successful long-term memory (LTM) depends upon effective control of information in working memory (WM), and there is evidence that both WM and LTM are impaired by schizophrenia. This study tests the hypothesis that LTM deficits in schizophrenia may result from impaired control of relational processing in WM due to dorsolateral prefrontal cortex (DLPFC) dysfunction. fMRI was performed on 19 healthy controls and 20 patients with schizophrenia during WM tasks emphasizing relational (reorder trials) versus item-specific (rehearse trials) processing. WM activity was also examined with respect to LTM recognition on a task administered outside the scanner. Receiver operator characteristic analysis assessed familiarity and recollection components of LTM. Patients showed a disproportionate familiarity deficit for reorder versus rehearse trials against a background of generalized LTM impairments. Relational processing during WM led to DLPFC activation in both groups. However, this activation was less focal in patients than in controls, and patients with more severe negative symptoms showed less of a DLPFC increase. fMRI analysis of subsequent recognition performance revealed a group by condition interaction. High LTM for reorder versus rehearse trials was associated with bilateral DLPFC activation in controls, but not in patients who activated the left middle temporal and inferior occipital gyrus. Results indicate that although patients can activate the DLPFC on a structured relational WM task, this activation is less focal and does not translate to high retrieval success, suggesting a disruption in the interaction between WM and LTM processes in schizophrenia.     

Neural correlates of combinatorial semantic processing of literal and figurative noun noun compound words

The right hemisphere's role in language comprehension is supported by results from several neuropsychology and neuroimaging studies. Special interest surrounds right temporoparietal structures, which are thought to be involved in processing novel metaphorical expressions, primarily due to the coarse semantic coding of concepts. In this event related fMRI experiment we aimed at assessing the extent of semantic distance processing in the comprehension of figurative meaning to clarify the role of the right hemisphere. Four categories of German noun noun compound words were presented in a semantic decision task: a) conventional metaphors; b) novel metaphors; c) conventional literal, and; d) novel literal expressions, controlled for length, frequency, imageability, arousal, and emotional valence. Conventional literal and metaphorical compounds increased BOLD signal change in right temporoparietal regions, suggesting combinatorial semantic processing, in line with the coarse semantic coding theory, but at odds with the graded salience hypothesis. Both novel literal and novel metaphorical expressions increased activity in left inferior frontal areas, presumably as a result of phonetic, morphosyntactic, and semantic unification processes, challenging predictions regarding right hemispheric involvement in processing unusual meanings. Meanwhile, both conventional and novel metaphorical expressions induced BOLD signal change in left hemispherical regions, suggesting that even novel metaphor processing involves more than linking semantically distant concepts.     

Neural correlates of cognitive efficiency

Since its inception, experimental psychology has sought to account for individual differences in human performance. Some neuroimaging research, involving complex behavioral paradigms, has suggested that faster-performing individuals show greater neural activity than slower performers. Other research has suggested that faster-performing individuals show less neural activity than slower performers. To examine the neural basis of individual performance differences, we had participants perform a simple speeded-processing task during fMRI scanning. In some prefrontal cortical (PFC) brain regions, faster performers showed less cortical activity than slower performers while in other PFC and parietal regions they showed greater activity. Regional-causality analysis indicated that PFC exerted more influence over other brain regions for slower than for faster individuals. These results suggest that a critical determinant of individual performance differences is the efficiency of interactions between brain regions and that slower individuals may require more prefrontal executive control than faster individuals to perform successfully.     

Neural correlates of memory confidence

The present study aimed to shed light on the neural underpinnings of high vs. low memory confidence. To dissociate memory confidence from accuracy, the Deese-Roediger McDermott (DRM) paradigm was employed, which - compared to other memory paradigms - elicits a rather evenly distributed number of high-confident responses across all possible combinations of memory response types (i.e., hits, false alarms, correct rejections, and misses). In the standard DRM procedure, subjects are first presented with thematically interrelated word lists at encoding, which at recognition are intermixed with related and unrelated distractor items. The signature of a false memory or DRM effect is an increased number of high-confident false memories, particularly for strongly related lure items. For the present study, 17 female subjects were administered a verbal DRM task, whereas neural activation was indexed by fMRI. The behavioral analyses confirmed the expected false memory effect: subjects made more high-confident old responses (both hits and false alarms) the closer the items were related to the central list theme. Across all four memory response types, an increase in confidence at recognition was associated with bilateral activation in the anterior and posterior cingulate cortex along with medial temporal regions. In contrast, increments in doubt were solely related to activation in the superior posterior parietal cortex. To conclude, the study provides some evidence for dissociable systems for confidence and doubt.     

Neural correlates of error awareness

Error processing results in a number of consequences on multiple levels. The posterior frontomedian cortex (pFMC) is involved in performance monitoring and signalling the need for adjustments, which can be observed as post-error speed-accuracy shifts at the behavioural level. Furthermore autonomic reactions to an error have been reported. The role of conscious error awareness for this processing cascade has received little attention of researchers so far. We examined the neural correlates of conscious error perception in a functional magnetic resonance imaging (fMRI) study. An antisaccade task known to yield sufficient numbers of aware and unaware errors was used. Results from a metaanalysis were used to guide a region of interest (ROI) analysis of the fMRI data. Consistent with previous reports, error-related activity in the rostral cingulate zone (RCZ), the pre-supplementary motor area (pre-SMA) and the insular cortex bilaterally was found. Whereas the RCZ activity did not differentiate between aware and unaware errors, activity in the left anterior inferior insular cortex was stronger for aware as compared to unaware errors. This could be due to increased awareness of the autonomic reaction to an error, or the increased autonomic reaction itself. Furthermore, post-error adjustments were only observed after aware errors and a correlation between post-error slowing and the hemodynamic activity in the RCZ was revealed. The data suggest that the RCZ activity alone is insufficient to drive error awareness. Its signal appears to be useful for post-error speed-accuracy adjustments only when the error is consciously perceived.     

Neuroanatomic/neuropathologic correlates in schizophrenia.

In the 1980s, numerous studies demonstrated neuropathologic changes in schizophrenia. Increased ventricle-brain ratios in schizophrenics have been reported. Birth-related trauma coupled with a genetic predisposition may be involved in the increased ventricle-brain ratios and in the development of some forms of the illness. Probable embryogenic anomalies in the hippocampus and other informational processing centers seem involved.     

Neural correlates of adjunctive rivastigmine treatment to antipsychotics in schizophrenia: a randomized, placebo-controlled, double-blind fMRI study

Facilitation of central cholinergic activity may form a potential treatment strategy for cognitive impairment in schizophrenia. In a randomized, placebo-controlled, double-blind, parallel-group design, we investigated the neural correlates of cognitive effects of rivastigmine, an acetylcholinesterase inhibitor, given as an add-on therapy to antipsychotic-treated schizophrenia patients. Thirty-six chronic schizophrenia patients with mild cognitive impairment took part. After 1 week on placebo (baseline), all patients entered a double-blind protocol; 18 were allocated to receive rivastigmine and 18 placebo for the next 12 weeks (final sample with usable imaging data: 11 patients on rivastigmine, 10 on placebo). All patients underwent functional magnetic resonance imaging during a parametric 'n-back' task, involving monitoring of dots in particular locations on a screen at a given delay from the original occurrence, twice: at baseline and 12 weeks post-rivastigmine/placebo treatment. Compared to placebo, rivastigmine produced only a small and non-significant improvement in task accuracy across all conditions with no change in response latency, and increased activity in the extrastriate visual cortex in areas associated with visual and spatial attention but not in any region within the working memory network. Our observations suggest that cholinergic enhancement with rivastigmine at doses known to be effective in Alzheimer's disease does not produce strong and clinically meaningful cognitive and neural changes in schizophrenia patients treated with atypical antipsychotics although the neural effects in terms of enhanced neuronal activity in regions associated with visual and spatial attention are consistent with those reported previously with cholinergic enhancement in healthy subjects.     

Neural correlates of processing situational relationships between a part and the whole: An fMRI study

Daily situations involve many objects and behaviors. To comprehend the meaning of situations, the relationships between objects, behaviors, and the situational context are important. To reveal the cortical networks involved in processing these relationships we used functional magnetic resonance imaging to compare brain activation during processing of behavior–situation and object–situation relationships. Each session examined two aspects of situational relationship processing: monitoring of the situational relationship and responses to irrelevant relationships. Monitoring was analyzed by comparing cortical activation during a situational relevance judgment task with that during a physical appropriateness judgment task. Responses were analyzed by comparing neural responses to situationally irrelevant and situationally relevant components. The left medial frontal cortex, fusiform gyrus, inferior frontal gyrus, calcarine sulcus, right anterior middle temporal gyrus, orbitoinsular junction, and occipito-temporo-parietal junction were commonly activated while monitoring relationships of both types. The right anterior middle temporal gyrus and orbitoinsular junction were considered to have roles in implicit monitoring because they were more deactivated during physical judgment tasks than during the resting state; this deactivation seemed to reflect unconscious situational monitoring in the resting state. Other regions seemed to be linked to explicit conscious monitoring. Responses to irrelevance were linked to separate and category-specific cortical activation in the left medial frontal cortex and frontal pole for behavioral irrelevance and in the left orbitofrontal cortex for irrelevant objects. We demonstrated that the hierarchical structure of processing situational relationships consisted of implicit monitoring, explicit monitoring, and category-specific responses to irrelevance.     

Neural correlates of artificial grammar learning

Artificial grammar learning (AGL) is a form of nondeclarative memory that involves the nonconscious acquisition of abstract rules. While data from amnesic patients indicate that AGL does not depend on the medial temporal lobe, the neural basis of this type of memory is unknown and was therefore examined using event-related fMRI. Prior to scanning, participants studied letter strings constructed according to an artificial grammar. Participants then made grammaticality judgments about novel grammatical and nongrammatical strings while fMRI data were collected. The participants successfully acquired knowledge of the grammar, as evidenced by correct identification of the grammatical letter strings (57.4% correct; SE 1.9). During grammaticality judgments, widespread increases in activity were observed throughout the occipital, posterior temporal, parietal, and prefrontal cortical areas, reflecting the cognitive demands of the task. More specific analyses contrasting grammatical and nongrammatical strings identified greater activity in left superior occipital cortex and the right fusiform gyrus for grammatical stimuli. Increased activity was also observed in the left superior occipital and left angular gyrus for correct responses compared to incorrect. Comparing activity during grammaticality judgments versus a matched recognition control task again identified greater activation in the left angular gyrus. The network of areas exhibiting increased activity for grammatical stimuli appears to have more in common with studies examining word-form processing or mental calculation than the fluency effects previously reported for nondeclarative memory tasks such as priming and visual categorization. These results suggest that a novel nondeclarative memory mechanism supporting AGL exists in the left superior occipital and inferior parietal cortex.     

Neural correlates of transformational apparent motion

When a figure discretely and instantaneously changes its shape, observers typically do not perceive the abrupt transition between shapes that in fact occurs. Rather, a continuous shape change is perceived. Although this illusory "transformational apparent motion" (TAM) is a faulty construction of the visual system, it is not arbitrary. From the many possible shape changes that could have been inferred, usually just one is perceived because only one is consistent with the shape-based rules that the visual system uses to (1) segment figures from one another within a scene and (2) match figures to themselves across successive scenes. TAM requires an interaction between neuronal circuits that process form relationships with circuits that compute motion trajectories. In particular, this form-motion interaction must happen before TAM is perceived because the direction of perceived motion is dictated by form relationships among figures in successive images. The present fMRI study (n = 19) provides the first evidence that both form (LOC, posterior fusiform gyrus) and motion (hMT+) processing areas are more active when TAM is perceived than in a control stimulus where it is not. Retinotopic areas (n = 10), hMT+ (n = 7), and LOC (n = 7) were mapped in a subset of subjects. Results: There is greater BOLD response to TAM than to the control condition in V1 and all subsequent retinotopic areas, as well as in hMT+ and the LOC, suggesting that areas that process form interact with hMT+ to construct the perception of moving figures.     

Error processing network dynamics in schizophrenia

Current theories of cognitive dysfunction in schizophrenia emphasize an impairment in the ability of individuals suffering from this disorder to monitor their own performance, and adjust their behavior to changing demands. Detecting an error in performance is a critical component of evaluative functions that allow the flexible adjustment of behavior to optimize outcomes. The dorsal anterior cingulate cortex (dACC) has been repeatedly implicated in error-detection and implementation of error-based behavioral adjustments. However, accurate error-detection and subsequent behavioral adjustments are unlikely to rely on a single brain region. Recent research demonstrates that regions in the anterior insula, inferior parietal lobule, anterior prefrontal cortex, thalamus, and cerebellum also show robust error-related activity, and integrate into a functional network. Despite the relevance of examining brain activity related to the processing of error information and supporting behavioral adjustments in terms of a distributed network, the contribution of regions outside the dACC to error processing remains poorly understood. To address this question, we used functional magnetic resonance imaging to examine error-related responses in 37 individuals with schizophrenia and 32 healthy controls in regions identified in the basic science literature as being involved in error processing, and determined whether their activity was related to behavioral adjustments. Our imaging results support previous findings showing that regions outside the dACC are sensitive to error commission, and demonstrated that abnormalities in brain responses to errors among individuals with schizophrenia extend beyond the dACC to almost all of the regions involved in error-related processing in controls. However, error related responses in the dACC were most predictive of behavioral adjustments in both groups. Moreover, the integration of this network of regions differed between groups, with the cerebellar regions and the dACC less connected to the network in individuals with schizophrenia compared to controls. Our findings demonstrate a blunted response to error commission in the dACC that is associated with reduced error-related behavioral adjustments in individuals with schizophrenia. This result supports the hypothesis that a failure to respond appropriately to errors in individuals with schizophrenia is linked to alterations in dACC function leading to a compromise in the implementation of cognitive control. Our findings highlight the importance of examining brain activity related to the processing of error information and supporting error-related behavioral adjustments in terms of a distributed network.     

Neural correlates of episodic retrieval success

Episodic memory retrieval involves multiple component processes, including those that occur when information is correctly remembered (retrieval success). The present study employed rapid-presentation event-related functional MRI that allowed different trial types with short intertrial intervals to be sorted such that the hemodynamic response associated with retrieval success could be extracted. Specifically, in an old/new episodic recognition task, hit trials (correctly recognized old items) and correct rejection trials (correctly rejected new items) were directly compared. The comparison revealed a mostly left-lateralized set of brain regions. Differential activation was most robust in left lateral parietal cortex and medial parietal cortex. Additional regions of differential activation included left anterior prefrontal cortex at or near Brodmann area 10, anterior insula, thalamus, anterior cingulate cortex, frontal cortex along inferior frontal gyrus, premotor cortex, and presupplementary motor area. These results suggest that left frontal and parietal regions modulate activity based on the successful retrieval of information from episodic memory. We discuss these findings in the context of several recent investigations that provide converging results as well as prior studies that have failed to detect these changes.     

Neural correlates of olfactory change detection

Detecting changes in a stream of sensory information is vital to animals and humans. While there have been several studies of automatic change detection in various sensory modalities, olfactory change detection is largely unstudied. We investigated brain regions responsive to both passive and active detection of olfactory change using fMRI. Nine right-handed healthy, normosmic subjects (five men) were scanned in two conditions while breathing in synchrony with a metronome. In one condition, subjects mentally counted infrequent odors (Attend condition), whereas in the other condition, subjects' attention was directed elsewhere as they counted auditory tones (Ignore condition). Odors were delivered via a nasal cannula using a computer-controlled air-dilution olfactometer. Infrequently occurring olfactory stimuli evoked significant (P < .05, corrected) activity in the subgenual cingulate and in central posterior orbitofrontal cortex, but only in the Ignore condition, as confirmed by direct comparison of the Ignore session with the Attend session (P < .05, corrected). Subgenual cingulate and posterior orbital cortex may therefore play a role in detecting discrepant olfactory events while attention is otherwise engaged in another sensory modality.     

Neural correlates of feigned memory impairment

While initial neuroimaging studies have provisionally identified activation in the prefrontal (including the anterior cingulate) and parietal regions during lying, the robustness of this neuroanatomical pattern of activation across forms of stimuli, genders, and mother tongues remains to be demonstrated. In this paper we report the results of three studies designed to test the reproducibility of the brain activation previously observed during feigned memory impairment. A total of twenty-nine right-handed participants, divided into three cohorts, participated in three different studies of feigned memory impairment. Findings indicate that bilateral activation of prefrontal and parietal regions was invariant across stimulus types, genders, and mother tongues, suggesting the general importance of these regions during malingering and possibly deception in general. In conjunction with earlier imaging findings, these three studies suggest that the prefrontal parietal network provides a robust neuroanatomical foundation upon which future dissimulation research may build.     

Neural correlates of the processing of another's mistakes: a possible underpinning for social and observational learning

Recent work suggests that a generalized error monitoring circuit, which shows heightened activation when one commits an error in goal-directed behavior, may exhibit synonymous activity when one watches another person commit a similar goal-directed error. In the present study, fMRI was utilized to compare and contrast those regions that show sensitivity to the performance, and to the observation, of committed errors. Participants performed a speeded go/no-go task and also observed a video of another person performing the same task. Dorsal anterior cingulate, orbitofrontal cortex, and supplementary motor regions were commonly activated to both performed and observed errors, providing evidence for common neural circuitry underlying the processing of one's own and another's mistakes. In addition, several regions, including inferior parietal cortex and anterorostral and ventral cinguli, did not show activation during performed errors, but were instead uniquely activated by the observation of another's mistakes. The unique nature of these 'observer-related' activations suggests that these regions, while of potential import towards recognition of another's errors, are not core to circuitry underlying error monitoring. Rather, we suggest that these regions may represent components of a distributed network important for the representation and interpretation of complex social actions.     

Neural correlates of age-related changes in cortical neurophysiology

Functional imaging studies of cortical motor systems in humans have demonstrated age-related reorganisation often attributed to anatomical and physiological changes. In this study we investigated whether aspects of brain activity during a motor task were influenced not only by age, but also by neurophysiological parameters of the motor cortex contralateral to the moving hand. Twenty seven right-handed volunteers underwent functional magnetic resonance imaging whilst performing repetitive isometric right hand grips in which the target force was parametrically varied between 15 and 55% of each subject's own maximum grip force. For each subject we characterised two orthogonal parameters, B(G) (average task-related activity for all hand grips) and B(F) (the degree to which task-related activity co-varied with peak grip force). We used transcranial magnetic stimulation (TMS) to assess task-related changes in interhemispheric inhibition from left to right motor cortex (IHIc) and to perform measures relating to left motor cortex excitability during activation of the right hand. Firstly, we found that B(G) in right (ipsilateral) motor cortex was greater with increasing values of age(2) and IHIc. Secondly, B(F) in left ventral premotor cortex was greater in older subjects and in those in whom contralateral M1 was less responsive to TMS stimulation. In both cases, neurophysiological parameters accounted for variability in brain responses over and above that explained by ageing. These results indicate that neurophysiological markers may be better indicators of biological ageing than chronological age and point towards the mechanisms by which reconfiguration of distributed brain networks occurs in the face of degenerative changes.     

Neural correlates of timbre change in harmonic sounds

Timbre is a major structuring force in music and one of the most important and ecologically relevant features of auditory events. We used sound stimuli selected on the basis of previous psychophysiological studies to investigate the neural correlates of timbre perception. Our results indicate that both the left and right hemispheres are involved in timbre processing, challenging the conventional notion that the elementary attributes of musical perception are predominantly lateralized to the right hemisphere. Significant timbre-related brain activation was found in well-defined regions of posterior Heschl's gyrus and superior temporal sulcus, extending into the circular insular sulcus. Although the extent of activation was not significantly different between left and right hemispheres, temporal lobe activations were significantly posterior in the left, compared to the right, hemisphere, suggesting a functional asymmetry in their respective contributions to timbre processing. The implications of our findings for music processing in particular and auditory processing in general are discussed.     

Neural correlates of continuous causal word generation

Causality provides a natural structure for organizing our experience and language. Causal reasoning during speech production is a distinct aspect of verbal communication, whose related brain processes are yet unknown. The aim of the current study was to investigate the neural mechanisms underlying the continuous generation of cause-and-effect coherences during overt word production. During fMRI data acquisition participants performed three verbal fluency tasks on identical cue words: A novel causal verbal fluency task (CVF), requiring the production of multiple reasons to a given cue word (e.g. reasons for heat are fire, sun etc.), a semantic (free association, FA, e.g. associations with heat are sweat, shower etc.) and a phonological control task (phonological verbal fluency, PVF, e.g. rhymes with heat are meat, wheat etc.). We found that, in contrast to PVF, both CVF and FA activated a left lateralized network encompassing inferior frontal, inferior parietal and angular regions, with further bilateral activation in middle and inferior as well as superior temporal gyri and the cerebellum. For CVF contrasted against FA, we found greater bold responses only in the left middle frontal cortex. Large overlaps in the neural activations during free association and causal verbal fluency indicate that the access to causal relationships between verbal concepts is at least partly based on the semantic neural network. The selective activation in the left middle frontal cortex for causal verbal fluency suggests that distinct neural processes related to cause-and-effect-relations are associated with the recruitment of middle frontal brain areas.