Lateral Frontal Cortex Research Articles

Longitudinal changes in cocaine intake and cognition are linked to cortical thickness adaptations in cocaine users.

BackgroundCocaine use has been consistently associated with decreased gray matter volumes in the prefrontal cortex. However, it is unclear if such neuroanatomical abnormalities depict either pre-existing vulnerability markers or drug-induced consequences. Thus, this longitudinal MRI study investigated neuroplasticity and cognitive changes in relation to altered cocaine intake.MethodsSurface-based morphometry, cocaine hair concentration, and cognitive performance were measured in 29 cocaine users (CU) and 38 matched controls at baseline and follow-up. Based on changes in hair cocaine concentration, CU were classified either as Decreasers (n = 15) or Sustained Users (n = 14). Surface-based morphometry measures did not include regional tissue volumes.ResultsAt baseline, CU displayed reduced cortical thickness (CT) in lateral frontal regions, and smaller cortical surface area (CSA) in the anterior cingulate cortex, compared to controls. In Decreasers, CT of the lateral frontal cortex increased whereas CT within the same regions tended to further decrease in Sustained Users. In contrast, no changes were found for CSA and subcortical structures. Changes in CT were linked to cognitive performance changes and amount of cocaine consumed over the study period.ConclusionsThese results suggest that frontal abnormalities in CU are partially drug-induced and can recover with decreased substance use. Moreover, recovery of frontal CT is accompanied by improved cognitive performance confirming that cognitive decline associated with cocaine use is potentially reversible.

Neural correlates of speech error monitoring and awareness

Neural correlates of speech error monitoring and awareness

Intrinsic Functional Boundaries of Lateral Frontal Cortex in the Common Marmoset Monkey.

The common marmoset (Callithrix jacchus) is a small New World primate species that has been recently targeted as a potentially powerful preclinical model of human prefrontal cortex dysfunction. Although the structural boundaries of frontal cortex were described in marmosets at the start of the 20th century (Brodmann, 1909) and refined more recently (Paxinos et al., 2012), the broad functional boundaries of marmoset frontal cortex have yet to be established. In this study, we sought to functionally derive boundaries of the marmoset lateral frontal cortex (LFC) using ultra-high field (9.4 T) resting-state functional magnetic resonance imaging (RS-fMRI). We collected RS-fMRI data in seven (four females, three males) lightly anesthetized marmosets and used a data-driven hierarchical clustering approach to derive subdivisions of the LFC based on intrinsic functional connectivity. We then conducted seed-based analyses to assess the functional connectivity between these clusters and the rest of the brain. The results demonstrated seven distinct functional clusters within the LFC. The functional connectivity patterns of these clusters with the rest of the brain were also found to be distinct and organized along a rostrocaudal gradient, consonant with those found in humans and macaques. Overall, these results support the view that marmosets are a promising preclinical modeling species for studying LFC dysfunction related to neuropsychiatric or neurodegenerative human brain diseases.SIGNIFICANCE STATEMENT The common marmoset is a New World primate that has garnered recent attention as a powerful complement to canonical Old World primate (e.g., macaques) and rodent models (e.g., rats, mice) for preclinical modeling of the human brain in healthy and diseased states. A critical step in the development of marmosets for such models is to characterize functional network topologies of frontal cortex in healthy, normally functioning marmosets, that is, how these circuitries are functionally divided and how those topologies compare to human circuitry. To our knowledge, this is the first study to demonstrate functional boundaries of the lateral frontal cortex and the corresponding network topologies in marmoset monkeys.

Dysfunctional Social Reinforcement Processing in Disruptive Behavior Disorders: An Functional Magnetic Resonance Imaging Study.

ObjectivePrior functional magnetic resonance imaging (fMRI) work has revealed that children/adolescents with disruptive behavior disorders (DBDs) show dysfunctional reward/non-reward processing of non-social reinforcements in the context of instrumental learning tasks. Neural responsiveness to social reinforcements during instrumental learning, despite the importance of this for socialization, has not yet been previously investigated.MethodsTwenty-nine healthy children/adolescents and 19 children/adolescents with DBDs performed the fMRI social/non-social reinforcement learning task. Participants responded to random fractal image stimuli and received social and non-social rewards/non-rewards according to their accuracy.ResultsChildren/adolescents with DBDs showed significantly reduced responses within the caudate and posterior cingulate cortex (PCC) to non-social (financial) rewards and social non-rewards (the distress of others). Connectivity analyses revealed that children/adolescents with DBDs have decreased positive functional connectivity between the ventral striatum (VST) and the ventromedial prefrontal cortex (vmPFC) seeds and the lateral frontal cortex in response to reward relative to non-reward, irrespective of its sociality. In addition, they showed decreased positive connectivity between the vmPFC seed and the amygdala in response to non-reward relative to reward.ConclusionThese data indicate compromised reinforcement processing of both non-social rewards and social non-rewards in children/adolescents with DBDs within core regions for instrumental learning and reinforcement-based decision-making (caudate and PCC). In addition, children/adolescents with DBDs show dysfunctional interactions between the VST, vmPFC, and lateral frontal cortex in response to rewarded instrumental actions potentially reflecting disruptions in attention to rewarded stimuli.

FMRI Response of Parietal Brain Areas to Sad Facial Stimuli in Mild Depression.

fMRI markers of mild depression were revealed using standard emotional test. Patients with mild depression and healthy volunteers were asked to determine gender of subjects in photographs with different emotional expressions (neutral, surprise, disgust, confusion, anger, sadness, fear, and joy). The pattern of response to different emotions was universal in both groups and included the largest clusters in the occipital region, as well as a certain volume in the parietal lobes and posterior lateral frontal cortex. In depression group, a lack of activation in the middle cingulate gyrus (bilaterally) and in the postcentral and inferior parietal gyrus (left) in response to presentation of sad faces. For other emotion, no large clusters of intergroup contrasts significant at p<0.05 with FWE correction were revealed. The response of the middle cingulate gyrus and the left inferior parietal lobe can be considered as a potential diagnostic marker of depressive disorders and as the target for neurofeedback.

Imaging Brain Metabolism in the Newborn.

In this review, we discuss molecular brain imaging studies using positron emission tomography (PET) with 2-deoxy-2(18F)fluoro-d-glucose (FDG) in human newborns and infants, and illustrate how this technology can be applied to probe the neuropathophysiology of neonatal neurologic disorders. PET studies have been difficult to perform in sick babies because of patient transportation issues and suboptimal spatial resolution. With approval from the FDA and the institutional review board, we modified and installed the Focus 220 animal microPET scanner (Concorde Microsystems, Knoxville, TN) directly in our neonatal intensive care unit in Children's Hospital of Michigan and verified the high spatial resolution (<2 mm full-width-at-half-maximum) of this microPET. The neonatal pattern of glucose metabolism is very consistent, with the highest degree of activity in primary sensory and motor cortex, medial temporal region, thalamus, brain stem, and cerebellar vermis. Prior studies have shown that increases of glucose utilization are seen by 2 to 3 months in the parietal, temporal, cingulate, and primary visual cortex; basal ganglia; and cerebellar hemispheres. Between 6 and 8 months, lateral and inferior frontal cortex becomes more functionally active and, eventually, between 8 and 12 months, the dorsal and medial frontal regions also show a maturational increase. These findings are consistent with the physical, behavioral, and cognitive maturation of the infant. At birth, metabolic rates of glucose utilization in cortex are about 30% lower than in adults but rapidly rise such that, by 3 years, the cerebral cortical rates exceed adult rates by more than 2-fold. At around puberty, the rates for cerebral cortex begin to decline and gradually reach adult values by 16-18 years. These nonlinear changes of glucose utilization indirectly reflect programed periods of synaptic proliferation and pruning in the brain. Positron emission tomographic (PET) imaging of GABAA receptors (using 11C-flumazenil) in newborns also show a pattern very different from adults, with high binding in amygdala-hippocampus, sensory-motor cortex, thalamus, brain stem, and basal ganglia, in that order. We speculate that the early development of amygdala/hippocampus prepares the baby for bonding, attachment, and memory, and the deprivation of such experiences during a sensitive period results in malfunction of these networks and psychopathology, as has been shown in studies on severely socioemotionally deprived children. Recently developed hybrid PET/magnetic resonance (MR) scanners allow the simultaneous acquisition of PET and MR data sets with advanced applications. These devices are particularly advantageous for scanning babies and infants because of the high spatial resolution, automated coregistration of anatomical and functional images and, in the case of need for sedation, maximal data acquired in 1 session.

Prediction of individualized task activation in sensory modality-selective frontal cortex with ‘connectome fingerprinting’

The human cerebral cortex is estimated to comprise 200–300 distinct functional regions per hemisphere. Identification of the precise anatomical location of an individual's unique set of functional regions is a challenge for neuroscience that has broad scientific and clinical utility. Recent studies have demonstrated the existence of four interleaved regions in lateral frontal cortex (LFC) that are part of broader visual attention and auditory attention networks (Michalka et al., 2015; Noyce et al., 2017; Tobyne et al., 2017). Due to a large degree of inter-subject anatomical variability, identification of these regions depends critically on within-subject analyses. Here, we demonstrate that, for both sexes, an individual's unique pattern of resting-state functional connectivity can accurately identify their specific pattern of visual- and auditory-selective working memory and attention task activation in lateral frontal cortex (LFC) using “connectome fingerprinting.” Building on prior techniques (Saygin et al., 2011; Osher et al., 2016; Tavor et al., 2016; Smittenaar et al., 2017; Wang et al., 2017; Parker Jones et al., 2017), we demonstrate here that connectome fingerprint predictions are far more accurate than group-average predictions and match the accuracy of within-subject task-based functional localization, while requiring less data. These findings are robust across brain parcellations and are improved with penalized regression methods. Because resting-state data can be easily and rapidly collected, these results have broad implications for both clinical and research investigations of frontal lobe function. Our findings also provide a set of recommendations for future research.

Neural processing of food cues in pre-pubertal children.

Neuroimaging investigations of brain pathways involved in reward and motivation have primarily focused on adults. This study sought to identify brain responses to visual food cues and explore its relationships with adiposity and sex in pre-pubertal children. Brain responses to palatable food vs. non-food cues were measured in 53 children (age: 8.18±.66years; sex: 22 boys, 31 girls) after an overnight fast. Whole-brain analysis (cluster-correction Z>2.3, P<.05) was performed to examine brain food cue reactivity and its relationships with adiposity and sex. Greater brain activity in response to food vs. non-food cues was observed in regions implicated in reward (orbital frontal cortex, striatum), taste (insula, postcentral gyrus), appetite (hypothalamus), emotion (amygdala), memory (hippocampus), visual processing (occipital cortex) and attention (parietal cortex). A negative association was found between percent body fat and food cue reactivity in the medial prefrontal cortex and lateral orbital frontal cortex adjusting for age and sex. Boys compared with girls had increased food cue reactivity in right hippocampus and visual cortex. These data suggest that body fat and sex are important moderators of brain food cue reactivity in children.

Structural and functional abnormality of the putamen in children with developmental dyslexia

There is currently debate with regards to the role of phonological deficit in Chinese reading difficulty, even though some researchers have suggested that the deficit of phonological processing is also a signature of developmental dyslexia in Chinese, as has been found in alphabetic languages. In this study, we examined the brain mechanisms of phonological deficit in Chinese children with developmental dyslexia (DD) during an auditory rhyming judgment task. First, we examined structural differences in Chinese dyslexia by comparing gray and white matter volume in Chinese children with DD, age-matched controls (AC), and reading-matched controls (RC). Next, we examined whether the regions with an abnormal volume in DD showed deficient functional connectivity with the rest of the brain during a phonological task (i.e. auditory rhyming judgment). We found that both AC and RC had greater gray matter volume (GMV) at the left putamen and right dorsal lateral frontal cortex than DD, suggesting possible neural signatures of developmental dyslexia. Functional connectivity analysis revealed that the left putamen was more connected with the right inferior occipital gyrus (IOG) in AC and RC than in DD, suggesting that automatic orthographic involvement during spoken language processing is more salient in controls, while the left putamen was more connected with the left transverse temporal gyrus (TTG) and left insula in DD than in AC and RC, suggesting the phonological articulation –auditory feedback loop is more involved in DD. These findings suggest that the reduced left putamen might contribute to phonological deficits experienced in DD, since it showed deficient connectivity with the rest of the brain during phonological processing.

Speech Registration in Symptomatic Memory Impairment.

Background: An inability to recall recent conversations often indicates impaired episodic memory retrieval. It may also reflect a failure of attentive registration of spoken sentences which leads to unsuccessful memory encoding. The hypothesis was that patients complaining of impaired memory would demonstrate impaired function of “multiple demand” (MD) brain regions, whose activation profile generalizes across cognitive domains, during speech registration in naturalistic listening conditions.Methods: Using functional MRI, brain activity was measured in 22 normal participants and 31 patients complaining of memory impairment, 21 of whom had possible or probable Alzheimer’s disease (AD). Participants heard a target speaker, either speaking alone or in the presence of distracting background speech, followed by a question to determine if the target speech had been registered.Results: Patients performed poorly at registering verbal information, which correlated with their scores on a screening test of cognitive impairment. Speech registration was associated with widely distributed activity in both auditory cortex and in MD cortex. Additional regions were most active when the target speech had to be separated from background speech. Activity in midline and lateral frontal MD cortex was reduced in the patients. A central cholinesterase inhibitor to increase brain acetylcholine levels in half the patients was not observed to alter brain activity or improve task performance at a second fMRI scan performed 6–11 weeks later. However, individual performances spontaneously fluctuated between the two scanning sessions, and these performance differences correlated with activity within a right hemisphere fronto-temporal system previously associated with sustained auditory attention.Conclusions: Midline and lateralized frontal regions that are engaged in task-dependent attention to, and registration of, verbal information are potential targets for transcranial brain stimulation to improve speech registration in neurodegenerative conditions.

Functional Networks for Social Communication in the Macaque Monkey

All primates communicate. To dissect the neural circuits of social communication, we used fMRI to map non-human primate brain regions for social perception, second-person (interactive) social cognition, and orofacial movement generation. Face perception, second-person cognition, and face motor networks were largely non-overlapping and acted as distinct functional units rather than an integrated feedforward-processing pipeline. Whereas second-person context selectively engaged a region of medial prefrontal cortex, production of orofacial movements recruited distributed subcortical and cortical areas in medial and lateral frontal and insular cortex. These areas exhibited some specialization, but not dissociation, of function along the medio-lateral axis. Production of lipsmack movements recruited areas including putative homologs of Broca's area. These findings provide a new view ofthe neural architecture for social communicationand suggest expressive orofacial movements generated by lateral premotor cortex as a putative evolutionary precursor to human speech.

Clinical Assessment of Prefrontal Lobe Functions.

Whereas it was previously thought that there was a single overarching frontal lobe syndrome, it is now clear that several distinct cognitive and behavioral processes are mediated by the frontal lobes. This article reviews these processes and the underlying neuroanatomy and provides an approach to the assessment of prefrontal lobe functions at the bedside. Cognitive and behavioral frontal lobe functions are mediated by the prefrontal regions rather than the frontal lobes as a whole. At least five separate prefrontal functions have been defined: energization, task setting, monitoring, behavioral/emotional regulation, and metacognition. Energization is mediated by the superior medial prefrontal cortices bilaterally, task setting by the left lateral frontal cortex, monitoring by the right lateral prefrontal cortex, behavioral/emotional regulation by the orbitofrontal cortex, and metacognition by the frontal poles. Only task setting and monitoring are considered executive functions. Distinct cognitive and behavioral processes are mediated by different parts of the frontal lobe. Lesions in these areas result in characteristic clinical deficits that are discussed in this article. Key messages are that prefrontal regions mediate the higher cortical functions (as opposed to the frontal lobes in general) and that prefrontal functions are not equivalent to executive functions.

Specializations for reward-guided decision-making in the primate ventral prefrontal cortex.

The estimated values of choices, and therefore decision-making based on those values, are influenced by both the chance that the chosen items or goods can be obtained (availability) and their current worth (desirability) as well as by the ability to link the estimated values to choices (a process sometimes called credit assignment). In primates, the prefrontal cortex (PFC) has been thought to contribute to each of these processes; however, causal relationships between particular subdivisions of the PFC and specific functions have been difficult to establish. Recent lesion-based research studies have defined the roles of two different parts of the primate PFC - the orbitofrontal cortex (OFC) and the ventral lateral frontal cortex (VLFC) - and their subdivisions in evaluating each of these factors and in mediating credit assignment during reward-based decision-making.

Entorhinal Cortex Volume Is Associated With Dual-Task Gait Cost Among Older Adults With MCI: Results From the Gait and Brain Study

BackgroundLow dual-task gait performance (the slowing of gait speed while performing a demanding cognitive task) is associated with low cognitive performance and an increased risk of progression to dementia in older adults with mild cognitive impairment. However, the reason for this remains unclear. This study aimed to examine the relationship between dual-task cost and regional brain volume, focusing on the hippocampus, parahippocampal gyrus, entorhinal cortex, and motor and lateral frontal cortices in older adults with mild cognitive impairment.MethodsForty older adults with mild cognitive impairment from the “Gait and Brain Study” were included in this study. Gait velocity was measured during single-task (ie, walking alone) and dual-task (ie, counting backwards, subtracting serial sevens, and naming animals, in addition to walking) conditions, using an electronic walkway. Regional brain volumes were derived by automated segmentation, using 3T magnetic resonance imaging.ResultsPartial rank correlation analyses demonstrated that a smaller volume of the left entorhinal cortex was associated with higher dual-task costs in counting backwards and subtracting serial sevens conditions. Subsequent logistic regression analyses demonstrated that a smaller volume of the left entorhinal cortex was independently associated with higher dual-task cost (slowing down >20% when performing cognitive task) in these two conditions. There were no other significant associations.ConclusionsOur results show that lower dual-task gait performance is associated with volume reduction in the entorhinal cortex. Cognitive and motor dysfunction in older adults with mild cognitive impairment may reflect a shared pathogenic mechanism, and dual-task-related gait changes might be a surrogate motor marker for Alzheimer’s disease pathology.

Brain Structural and Functional Substrates of Personal Distress in Empathy.

Empathy is the capacity to understand and experience the feeling state of others. While individuals attribute negative empathic responses to their own feelings, they would endure personal distress that can be harmful to social interaction. However, the neural mechanism of personal distress remains unclear. Here, we examined the neural substrates of personal distress by combining structural (Voxel-based morphometry (VBM)) and functional (resting-state functional connectivity (FC) analysis) MRI approaches in 53 college students (aged 19–26). A negative correlation was found between a trait measure of personal distress and gray matter (GM) volume in the dorsal medial prefrontal cortex (dmPFC). FC analyses with the dmPFC as a seed further revealed that the connectivity between the dmPFC and posterior insula was positively correlated with the personal distress, and the connectivities between the dmPFC and the anterior middle cingulate cortex, left lateral frontal cortex, and left inferior parietal gyrus were negatively correlated with the personal distress. Our results suggested that personal distress is underlain by neural substrates associated with both cognitive and affective mechanisms. Taken together, the structural and functional correlates of personal distress revealed in the present findings shed new light into the understanding of empathy.

Flow experience and the mobilization of attentional resources.

The present study attempts to better identify the neurophysiological changes occurring during flow experience and how this can be related to the mobilization of attentional resources. Self-reports of flow (using a flow feelings scale) and attention (using thought probes), autonomic activity (heart rate, heart rate variability, and breathing rate), and cerebral oxygenation (using near-infrared spectroscopy) in two regions of the frontoparietal attention network (right lateral frontal cortex and right inferior parietal lobe) were measured during the practice of two simple video games (Tetris and Pong) played at different difficulty conditions (easy, optimal, hard, or self-selected). Our results indicated that an optimal level of difficulty, compared with an easy or hard level of difficulty led to greater flow feelings and a higher concentration of oxygenated hemoglobin in the regions of the frontoparietal network. The self-selected, named autonomy condition did not lead to more flow feelings than the optimal condition; however, the autonomy condition led to greater sympathetic activity (reduced heart rate variability and greater breathing rate) and higher activation of the frontoparietal regions. Our study suggests that flow feelings are highly connected to the mobilization of attentional resources, and all the more in a condition that promotes individuals' choice and autonomy.

Aberrant dynamics of spontaneous brain activity and its integration in patients with autism spectrum disorder

Autism spectrum disorder (ASD) is a neurodevelopmental disease with unknown etiology but high incidence. The objective biomarkers of ASD are urgently awaited to be developed using neuroimaging method including resting-state fMRI (R-fMRI). However, the majority of current R-fMRI studies only examined the static features of brain activity in ASD patients, but neglected the dynamic aspects especially for regional metrics. Furthermore, the concordance of the dynamic regional indices was reported imbedded in human intrinsic brain activity, while its abnormality in ASD is largely unknown. In order to shed light on the abnormity of ASD from dynamic perspective, we analyzed R-fMRI data of 480 ASD male patients and 539 healthy male controls (HC) gathered from ASD public database (ABIDE I/ABIDE II). We used sliding window method to calculate the dynamics of mainstream regional indices of R-fMRI (amplitude of low frequency fluctuations (ALFF), fractional ALFF (fALFF), regional homogeneity (ReHo), voxel-mirrored homotopic connectivity (VMHC), degree centrality (DC) and the correlation with global signal (GSCorr)) and generated the SD statistic maps of these six dynamic regional indices. We performed z-standardization and smoothing on the SD statistic maps. After that, two-sample t -test between the SD statistic maps of ASD group and HC group was performed. We also calculated the concordance of dynamic regional indices for each time point, which is the Kendall’s coefficient of the ALFF, ReHo, DC, GSCorr and VMHC maps across voxels. Two-sample t -test between the SD and mean of concordance time series of ASD group and HC group was performed. We found a significant increase in the dynamics of ALFF and DC in the lateral frontal cortices in ASD patients as compared to HCs. Dorsal lateral frontal cortex (dlPFC) is a critical brain area for cognitive control and execution network. The abnormal activities in dlPFC indicate the disruption of control execution system and the impairment of relevant cognitive function. In the visual related brain areas, the dynamics of ALFF, DC and ReHo showed a decrease in fusiform gyrus, calcarine and lingual gyrus in ASD patients. Recent studies have indicated that the abnormal face processing in children with autism may be related with the impairment in social cognition of them. The deficits in face information processing of ASD patients may stem from the inflexible intrinsic brain activity in visual processing brain area (especially in fusiform gyrus). After further examining the concordance among these dynamic indices, the mean and SD of concordance of patients with ASD was found to be significantly lower than that of the HCs, demonstrating that the ASD patients’ inferior integration ability for different aspects of brain functions. These findings suggest that there exists abnormality in dynamics of spontaneous brain activity and its integration in ASD patients. Dynamic R-fMRI regional indices and the concordance of them could be efficient neuroimaging biomarkers for ASD.

Inferior Parietal Cortex Hypoperfusion is the Most Specific Imaging Marker for AD Patients With Positive CSF Biomarker Assays in a Memory Clinic in France.

The diagnostic accuracy of hexamethylpropyleneamine oxime (HMPAo) single-photon emission computed tomography (SPECT) in Alzheimer disease (AD) remains undetermined in a "real-life" clinical population. The objective was to determine the HMPAo SPECT hypoperfusion pattern in cognitively impaired patients with positive CSF AD biomarker and to evaluate its diagnostic accuracy. This study included 120 patients referred to a university memory clinic assessed using HMPAo SPECT, MRI, and CSF biomarkers. Three biomarker signatures suggestive of AD were analyzed (1, Aß1-42; 2, Aß1-42+t-tau and/or p-tau; 3, Aß1-42/p-tau). The clinical diagnoses were possible AD (n=29) or other causes of cognitive impairment (n=91). All CSF AD signatures were significantly (1, P=0.004; 2, P=0.017; 3, P=0.024) associated with the difference between inferior parietal perfusion and lateral dorsal frontal cortex perfusion. The hypoperfusion pattern discriminated between patients with positive CSF AD biomarkers and those with other cognitive impairments with a sensitivity of 67% to 71% and a specificity of 63% to 65% and a greatest negative predictive value (NPV) of 90%. Inferior parietal cortex hypoperfusion was the most sensitive and specific feature in AD patients diagnosed using clinical and CSF biomarker criteria. This hypoperfusion pattern was associated with an NPV of 90% and therefore discriminated sharply between AD and other cognitive disorders.

Using functional near-infrared spectroscopy to assess auditory attention

Speech intelligibility in background sound can improve when listeners attend to the target. Using functional magnetic resonance imaging, previous work demonstrates that auditory attention alters Blood Oxygenation Level Dependent (BOLD) signals in the lateral frontal cortex (LFCx; Michalka et al., Neuron 2015), at least when directed to spatial cues. Using functional near-infrared spectroscopy (fNIRS), we recorded BOLD responses from LFCx in 54 normal-hearing participants, each performing one of three auditory experiments. The weights of general linear modeling (GLM) fits of the fNIRS recordings were compared using analysis of variance. In experiment 1, when listeners selectively attended to stimuli differing in pitch and space, both left and right LFCx showed significant activation (p = 0.01 and 0.02 for left versus right LFCx). In contrast, passive listening to speech-shaped noise did not cause significant changes in LFCx activation (p = 0.3 and p 0.1 for left versus right LFCx). Experiment 2 confirmed these results, revealing comparable fNIRS traces when attending to pitch alone, versus attending to space and pitch. Experiment 3 further strengthened these results by controlling for eye movements. Result suggests that fNIRS is a viable tool for assessing whether or not a listener deploys auditory attention to perform a task.

Transient and sustained ERP activity related to feedback processing in the probabilistic selection task

Feedback processing represents a fundamental component of adaptive decision-making. Extensive research using event-related brain potentials (ERPs) has explored the medial frontal feedback negativity (FN), P3a, and P3b components in the context of feedback processing. Additionally, recent studies examining the neural correlates of feedback processing in a gambling task revealed transient and sustained ERP activity over the lateral frontal and posterior regions of the scalp. Consistent with the neuroimaging literature, source analysis has localized this ERP activity to the lateral and medial frontal cortex, as well as the temporal-occipital and medial occipital cortices. The current experiments examine whether the pattern of transient medial frontal and sustained lateral frontal and posterior ERP activity extend to a reinforcement learning task, and may thereby represent a general property of feedback processing. Consistent with a large literature, the ERP data revealed the FN-P3a and P3b. In addition, these data revealed sustained ERP activity over the lateral frontal and posterior regions. These findings contribute to our understanding of the temporal dynamics of feedback processing across broadly distributed cortical and subcortical networks that are sensitive to the valence and probability of positive and negative outcomes.