Frontal Eye Field Activity Research Articles

Task-switching mechanisms under methamphetamine cravings: sex differences in cued and voluntary task-switching.

This study explored the effects of task-switching type and sex on the task-switching ability of methamphetamine abstainers, as well as the differences in brain mechanisms under drug cravings under drug cravings using near-infrared spectroscopy. Craving-inducing videos were used to arouse 20 methamphetamine abstainers (including 10 men), whose switching ability was then assessed using voluntary and cued task-switching exercises. During task-switching under methamphetamine cravings, the activation of the premotor cortex (PMC), supplementary motor area (SMA), frontal eye field (FEF), and dorsolateral prefrontal cortex (DLPFC) in women was significantly stronger than in men, while the activation of FEF in men was significantly stronger than in women. Voluntary task-switching induced stronger FEF activation than cued task-switching. During the latter, women exhibited stronger activation in the anterior prefrontal cortex (aPFC) than men. Both men and women showed brain lateralization during task-switching under methamphetamine cravings. Men tended to adopt proactive control and use a top-down dominant strategy to start a new task. Women, however, tend to use a bottom-up strategy focusing on inhibiting old tasks and emotional switching. Moreover, in cued task-switching, the result shows women paid more attention to emotional processing than did men, which suggests that different task-switching training programs should be developed according to sex.

Dynamics of Saccade Trajectory Modulation by Distractors: Neural Activity Patterns in the Frontal Eye Field.

The sudden appearance of a visual distractor shortly before saccade initiation can capture spatial attention and modulate the saccade trajectory in spite of the ongoing execution of the initial plan to shift gaze straight to the saccade target. To elucidate the neural correlates underlying these curved saccades, we recorded from single neurons in the frontal eye field (FEF) of two male rhesus monkeys shifting gaze to a target while a distractor with the same eccentricity appeared either left or right of the target at various delays after target presentation. We found that the population level of pre-saccadic activity of neurons representing the distractor location encoded the direction of the saccade trajectory. Stronger activity occurred when saccades curved toward the distractor, and weaker when saccades curved away. This relationship held whether the distractor was ipsilateral or contralateral to the recorded neurons. Meanwhile, visually responsive neurons showed asymmetrical patterns of excitatory responses that varied with the location of the distractor and the duration of distractor processing relating to attentional capture and distractor inhibition. During earlier distractor processing, neurons encoded curvature towards the distractor. During later distractor processing, neurons encoded curvature away from the distractor. This was observed when saccades curved away from distractors contralateral to the recording site and when saccades curved towards distractors ipsilateral to the recording site. These findings indicate that saccadic motor planning involves dynamic push-pull hemispheric interactions producing attraction or repulsion for potential but unselected saccade targets.Significant Statement This study not only advances our understanding of oculomotor function in dynamic environments but also has potential clinical relevance for diagnosing and understanding disorders characterized by abnormal saccade trajectories. Our research elucidates the neural mechanisms behind saccade trajectories that are not always linear due to the brain's integration of multiple visual cues and/or motor plans. By analyzing the frontal eye field (FEF) activity in rhesus monkeys, we found that saccade directionality and timing are influenced by the interaction between FEF visual neurons representing target and distractor stimuli. The FEF's role extends beyond a winner-takes-all approach, incorporating saccade vector averaging computations that produce curved saccades. Furthermore, ipsilateral visual neurons encode distractor suppression that drives curvature away from the distractor.

Chronic cannabis use alters the spontaneous and oscillatory gamma dynamics serving cognitive control.

Regular cannabis use is associated with cortex-wide changes in spontaneous and oscillatory activity, although the functional significance of such changes remains unclear. We hypothesized that regular cannabis use would suppress spontaneous gamma activity in regions serving cognitive control and scale with task performance. Participants (34 cannabis users, 33 nonusers) underwent an interview regarding their substance use history and completed the Eriksen flanker task during magnetoencephalography (MEG). MEG data were imaged in the time-frequency domain and virtual sensors were extracted from the peak voxels of the grand-averaged oscillatory interference maps to quantify spontaneous gamma activity during the pre-stimulus baseline period. We then assessed group-level differences in spontaneous and oscillatory gamma activity, and their relationship with task performance and cannabis use metrics. Both groups exhibited a significant behavioral flanker interference effect, with slower responses during incongruent relative to congruent trials. Mixed-model ANOVAs indicated significant gamma-frequency neural interference effects in the left frontal eye fields (FEF) and left temporoparietal junction (TPJ). Further, a group-by-condition interaction was detected in the left FEF, with nonusers exhibiting stronger gamma oscillations during incongruent relative to congruent trials and cannabis users showing no difference. In addition, spontaneous gamma activity was sharply suppressed in cannabis users relative to nonusers in the left FEF and TPJ. Finally, spontaneous gamma activity in the left FEF and TPJ was associated with task performance across all participants, and greater cannabis use was associated with weaker spontaneous gamma activity in the left TPJ of the cannabis users. Regular cannabis use was associated with weaker spontaneous gamma in the TPJ and FEF. Further, the degree of use may be proportionally related to the degree of suppression in spontaneous activity in the left TPJ.

Activation of primate frontal eye fields with a CMUT phased array system

BackgroundThere are pushes toward non-invasive stimulation of neural tissues to prevent issues that arise from invasive brain recordings and stimulation. Transcranial Focused Ultrasound (TFUS) has been examined as a way to stimulate non-invasively, but previous studies have limitations in the application of TFUS. As a result, refinement is needed to improve stimulation results. New MethodWe utilized a custom-built capacitive micromachined ultrasonic transducer (CMUT) that would send ultrasonic waves through skin and skull to targets located in the Frontal Eye Fields (FEF) region triangulated from co-registered MRI and CT scans while a non-human primate subject was performing a discrimination behavioral task. ResultsWe observed that the stimulation immediately caused changes in the local field potential (LFP) signal that continued until stimulation ended, at which point there was higher voltage upon the cue for the animal to saccade. This co-incided with increases in activity in the alpha band during stimulation. The activity rebounded mid-way through our electrode-shank, indicating a specific point of stimulation along the shank. We observed different LFP signals for different stimulation targets, indicating the ability to“steer” the stimulation through the transducer. We also observed a bias in first saccades towards the opposite direction. ConclusionsIn conclusion, we provide a new approach for non-invasive stimulation during performance of a behavioral task. With the ability to steer stimulation patterns and target using a large amount of transducers, the ability to provide non-invasive stimulation will be greatly improved for future clinical and research applications.

Dissociating the Contributions of Frontal Eye Field Activity to Spatial Working Memory and Motor Preparation.

Neurons within dorsolateral prefrontal cortex (PFC) of primates are characterized by robust persistent spiking activity exhibited during the delay period of working memory tasks. This includes the frontal eye field (FEF) where nearly half of the neurons are active when spatial locations are held in working memory. Past evidence has established the FEF's contribution to the planning and triggering of saccadic eye movements as well as to the control of visual spatial attention. However, it remains unclear whether persistent delay activity reflects a similar dual role in movement planning and visuospatial working memory. We trained male monkeys to alternate between different forms of a spatial working memory task which could dissociate remembered stimulus locations from planned eye movements. We tested the effects of inactivation of FEF sites on behavioral performance in the different tasks. Consistent with previous studies, FEF inactivation impaired the execution of memory-guided saccades (MGSs), and impaired performance when remembered locations matched the planned eye movement. In contrast, memory performance was largely unaffected when the remembered location was dissociated from the correct eye movement response. Overall, the inactivation effects demonstrated clear deficits in eye movements, regardless of task type, but little or no evidence of a deficit in spatial working memory. Thus, our results indicate that persistent delay activity in the FEF contributes primarily to the preparation of eye movements and not to spatial working memory.SIGNIFICANCE STATEMENT Many frontal eye field (FEF) neurons exhibit spatially tuned persistent spiking activity during the delay period of working memory tasks. However, the role of the FEF in spatial working memory remains unresolved. We tested the effects of inactivation of FEF sites on behavioral performance in different forms of a spatial working memory task, one of which dissociated the remembered stimulus locations from planned eye movements. We found that FEF inactivation produced clear deficits in eye movements, regardless of task type, but no deficit in spatial working memory when dissociated from those movements.

Dynamic encoding of saccade sequences in primate frontal eye field.

The frontal eye field (FEF) is a key part of the oculomotor system, with dominant responses to the direction of single saccades. However, whether and how FEF contributes to sequential saccades remain largely unknown. By training rhesus monkeys to perform saccade sequences, we found sequence-related activities in FEF neurons, whose selectivity to saccade direction undergoes dynamic changes during sequential vs. single saccades. These sequence-related activities are context-dependent, exhibiting different firing activities during memory- vs. visually guided sequences. When the monkey was performing the sequential saccade task, the thresholds of microstimulation to evoke saccades in FEF were increased and the percentage of the successfully induced saccades was significantly reduced compared with the fixation condition. Pharmacological inactivation of FEF impaired the monkey's performance of previously learned sequential saccades, with different effects on the same actions depending on its position within the sequence. These results reveal the context-dependent, sequence-specific dynamic encoding of saccades in FEF, and underscore the crucial role of FEF in the planning and execution of sequential saccades. KEY POINTS: FEF neurons respond differently during sequential vs. single saccades Sequence-related FEF activity is context-dependent The microstimulation threshold in FEF was increased during the sequential task but the evoked saccade did not alter the sequence structure FEF inactivation severely impaired the performance of sequential saccades.

The roles of the lateral intraparietal area and frontal eye field in guiding eye movements in free viewing search behavior.

The lateral intraparietal area (LIP) and frontal eye field (FEF) have been shown to play significant roles in oculomotor control, yet most studies have found that the two areas behave similarly. To identify the unique roles each area plays in guiding eye movements, we recorded 200 LIP neurons and 231 FEF neurons from four animals performing a free viewing visual foraging task. We analyzed how neuronal responses were modulated by stimulus identity and the animals' choice of where to make a saccade. We additionally analyzed the comodulation of the sensory signals and the choice signal to identify how the sensory signals drove the choice. We found a clearly defined division of labor: LIP provided a stable map integrating task rules and stimulus identity, whereas FEF responses were dynamic, representing more complex information and, just before the saccade, were integrated with task rules and stimulus identity to decide where to move the eye.NEW & NOTEWORTHY The lateral intrapareital area (LIP) and frontal eye field (FEF) are known to contribute to guiding eye movements, but little is known about the unique roles that each area plays. Using a free viewing visual search task, we found that LIP provides a stable map of the visual world, integrating task rules and stimulus identity. FEF activity is consistently modulated by more complex information but, just before the saccade, integrates all the information to make the final decision about where to move.

Top-down control of visual cortex by the frontal eye fields through oscillatory realignment

Voluntary allocation of visual attention is controlled by top-down signals generated within the Frontal Eye Fields (FEFs) that can change the excitability of lower-level visual areas. However, the mechanism through which this control is achieved remains elusive. Here, we emulated the generation of an attentional signal using single-pulse transcranial magnetic stimulation to activate the FEFs and tracked its consequences over the visual cortex. First, we documented changes to brain oscillations using electroencephalography and found evidence for a phase reset over occipital sites at beta frequency. We then probed for perceptual consequences of this top-down triggered phase reset and assessed its anatomical specificity. We show that FEF activation leads to cyclic modulation of visual perception and extrastriate but not primary visual cortex excitability, again at beta frequency. We conclude that top-down signals originating in FEF causally shape visual cortex activity and perception through mechanisms of oscillatory realignment.

Neural correlates of goal-directed and non-goal-directed movements.

What are the cortical neural correlates that distinguish goal-directed and non-goal-directed movements? We investigated this question in the monkey frontal eye field (FEF), which is implicated in voluntary control of saccades. Here, we compared FEF activity associated with goal-directed (G) saccades and non-goal-directed (nG) saccades made by the monkey. Although the FEF neurons discharged before these nG saccades, there were three major differences in the neural activity: First, the variability in spike rate across trials decreased only for G saccades. Second, the local field potential beta-band power decreased during G saccades but did not change during nG saccades. Third, the time from saccade direction selection to the saccade onset was significantly longer for G saccades compared with nG saccades. Overall, our results reveal unexpected differences in neural signatures for G versus nG saccades in a brain area that has been implicated selectively in voluntary control. Taken together, these data add critical constraints to the way we think about saccade generation in the brain.

Single-Case Neuropsychological Assessment of a Patient with a Posterior Parietal Lesion Using Behavioral Testing and Resting-State fMRI

This study integrated functional connectivity measures using resting-state fMRI and behavioral data from a single-case observation of patient (PER) one year after right-hemispheric hemorrhage in the intraparietal sulcus and superior parietal lobule (IPS/SPL). PER showed no sign of clinical neglect. Her behavioral performance in the visuo-manual pointing task and in the letter discrimination task under conditions of endogenous and exogenous attentional cueing was compared between the left (affected) and right (unaffected/control) peripheral visual fields. The resting-state fMRI demonstrated an imbalance between the right and left hemispheric frontoparietal functional connectivity within the dorsal attentional and motor networks. Although the frontal and occipital cortices were not structurally damaged, specific fronto-occipital functional connectivity was imbalanced, which was strongly associated with the behavioral changes. First, the activity in the right frontal eye field showed weaker correlations with the activity in the right inferior occipital area compared to the correlation with the activity in the left inferior occipital area. This imbalanced fronto-occipital functional connectivity was accompanied by a specific impairment in endogenous covert attention in the left visual field. Second, the activity within M1 in both hemispheres showed weaker correlations with the activity of the right cuneus compared to the correlation with the activity in the left cuneus. The imbalanced fronto-occipital functional connectivity was associated with the impairment of the reaching movement of the left and right hands towards the left visual field (optic ataxia). Altogether, our results showed that a lesion to the posterior parietal cortex affects the relationship between distal regions underlying the sensorimotor and attentional abilities

Frontal eye field and caudate neurons make different contributions to reward-biased perceptual decisions.

Many decisions require trade-offs between sensory evidence and internal preferences. Potential neural substrates include the frontal eye field (FEF) and caudate nucleus, but their distinct roles are not understood. Previously we showed that monkeys' decisions on a direction-discrimination task with asymmetric rewards reflected a biased accumulate-to-bound decision process (Fan et al., 2018) that was affected by caudate microstimulation (Doi et al., 2020). Here we compared single-neuron activity in FEF and caudate to each other and to accumulate-to-bound model predictions derived from behavior. Task-dependent neural modulations were similar in both regions. However, choice-selective neurons in FEF, but not caudate, encoded behaviorally derived biases in the accumulation process. Baseline activity in both regions was sensitive to reward context, but this sensitivity was not reliably associated with behavioral biases. These results imply distinct contributions of FEF and caudate neurons to reward-biased decision-making and put experimental constraints on the neural implementation of accumulation-to-bound-like computations.

Differences in Noradrenaline Receptor Expression Across Different Neuronal Subtypes in Macaque Frontal Eye Field.

Cognitive functions such as attention and working memory are modulated by noradrenaline receptors in the prefrontal cortex (PFC). The frontal eye field (FEF) has been shown to play an important role in visual spatial attention. However, little is known about the underlying circuitry. The aim of this study was to characterize the expression of noradrenaline receptors on different pyramidal neuron and inhibitory interneuron subtypes in macaque FEF. Using immunofluorescence, we found broad expression of noradrenaline receptors across all layers of the FEF. Differences in the expression of different noradrenaline receptors were observed across different inhibitory interneuron subtypes. No significant differences were observed in the expression of noradrenaline receptors across different pyramidal neuron subtypes. However, we found that putative long-range projecting pyramidal neurons expressed all noradrenaline receptor subtypes at a much higher proportion than any of the other neuronal subtypes. Nearly all long-range projecting pyramidal neurons expressed all types of noradrenaline receptor, suggesting that there is no receptor-specific machinery acting on these long-range projecting pyramidal neurons. This pattern of expression among long-range projecting pyramidal neurons suggests a mechanism by which noradrenergic modulation of FEF activity influences attention and working memory.

Cortical activity during social acceptance and rejection task in social anxiety disorder: A controlled functional near infrared spectroscopy study

BackgroundThe cognitive and emotional vulnerability of individuals with social anxiety disorder (SAD) and their response to repeated experiences of social rejection and social acceptance are important factors for the emergence and maintenance of symptoms of the disorder. Functional neuroimaging studies of SAD reveal hyperactivity in regions involved in the fear circuit such as amygdala, insula, anterior cingulate, and prefrontal cortices (PFC) in response to human faces with negative emotions. Observation of brain activity, however, involving studies of responses to standardized human interaction of social acceptance and social rejection have been lacking. MethodsWe compared a group of index subjects with SAD (N = 22, mean age:26.3 ± 5.4, female/male: 7/15) (SADG) with a group of healthy controls (CG) (N = 21, mean age:28.7 ± 4.5, female/male: 14/7) in measures of cortical activity during standardized experiences of human interaction involving social acceptance (SA) and social rejection (SR) video-simulated handshaking tasks performed by real actors. In a third, control condition (CC), the subjects were expected to press a switch button in an equivalent space. Subjects with a concurrent mood episode were excluded and the severity of subclinical depressive symptoms was controlled. 52-channel functional near-infrared spectroscopy (fNIRS) was used to measure cortical activity. ResultsActivity was higher in the SAD subjects compared to healthy controls, in particular in channels that project to middle and superior temporal gyri (STG), frontal eye fields (FEF) and dorsolateral prefrontal cortex (DLPFC) in terms of both SA and SR conditions. Cortical activity during the CC was not different between the groups. Only in the SAD-group, activity in the pre-motor and supplementary motor cortices, inferior and middle temporal gyri and fronto-polar area was higher during the rejection condition than the other two conditions. Anxiety scores were correlated with activity in STG, DLPFC, FEF and premotor cortex, while avoidance scores were correlated with activity in STG and FEF. ConclusionsSA and SR are represented differently in terms of cortical activity in SAD subjects compared to healthy controls. Higher activity in both social conditions in SAD subjects compared to controls may imply biological sensitivity to these experiences and may underscore the importance of increased cortical activity during social interaction experiences as a putative mediator of vulnerability to SAD. Higher cortical activity in the SADG may possibly indicate stronger need for inhibitory control mechanisms and higher recruitment of theory of mind functions during social stress. Higher activity during the SR compared to the SA condition in the SAD subjects may also suggest distinct processing of social cues, whether they involve acceptance or rejection.

Integration of Eye-Centered and Landmark-Centered Codes in Frontal Eye Field Gaze Responses.

The visual system is thought to separate egocentric and allocentric representations, but behavioral experiments show that these codes are optimally integrated to influence goal-directed movements. To test if frontal cortex participates in this integration, we recorded primate frontal eye field activity during a cue-conflict memory delay saccade task. To dissociate egocentric and allocentric coordinates, we surreptitiously shifted a visual landmark during the delay period, causing saccades to deviate by 37% in the same direction. To assess the cellular mechanisms, we fit neural response fields against an egocentric (eye-centered target-to-gaze) continuum, and an allocentric shift (eye-to-landmark-centered) continuum. Initial visual responses best-fit target position. Motor responses (after the landmark shift) predicted future gaze position but embedded within the motor code was a 29% shift toward allocentric coordinates. This shift appeared transiently in memory-related visuomotor activity, and then reappeared in motor activity before saccades. Notably, fits along the egocentric and allocentric shift continua were initially independent, but became correlated across neurons just before the motor burst. Overall, these results implicate frontal cortex in the integration of egocentric and allocentric visual information for goal-directed action, and demonstrate the cell-specific, temporal progression of signal multiplexing for this process in the gaze system.

Causal contributions of human frontal eye fields to distinct aspects of decision formation

Several theories propose that perceptual decision making depends on the gradual accumulation of information that provides evidence in favour of one of the choice-options. The outcome of this temporally extended integration process is thought to be categorized into the ‘winning’ and ‘losing’ choice-options for action. Neural correlates of corresponding decision formation processes have been observed in various frontal and parietal brain areas, among them the frontal eye-fields (FEF). However, the specific functional role of the FEFs is debated. Recent studies in humans and rodents provide conflicting accounts, proposing that the FEF either accumulate the choice-relevant information or categorize the outcome of such evidence integration into discrete actions. Here, we used transcranial magnetic stimulation (TMS) on humans to interfere with either left or right FEF activity during different timepoints of perceptual decision-formation. Stimulation of either FEF affected performance only when delivered during information integration but not during subsequent categorical choice. However, the patterns of behavioural changes suggest that the left-FEF contributes to general evidence integration, whereas right-FEF may direct spatial attention to the contralateral hemifield. Taken together, our results indicate an FEF involvement in evidence accumulation but not categorization, and suggest hemispheric lateralization for this function in the human brain.

Reliability of Frontal Eye Fields Activation and Very Low-Frequency Oscillations Observed during Vergence Eye Movements: an fNIRS Study

Functional near-infrared spectroscopy (fNIRS), an imaging tool that utilizes infrared light to measure changes within the concentration of oxygenated (HbO) and deoxygenated (HbR) hemoglobin, holds promise to study functional activity from motor, visual, and memory cortical regions using stimulus-induced tasks. This study investigated the reliability for fNIRS to examine cortical activations within the frontal eye fields (FEF) while initiating vergence eye movements, the inward and outward rotation of the eyes. FNIRS data were collected from twenty participants with normal binocular vision while performing vergence eye movements compared to sustained gaze fixation within a block design during two different sessions. Reliability of the experimental protocol was assessed using the intraclass correlation coefficient (ICC). The ICC values ranged from 0.6 to 0.7 for measuring the HbO activation within the vicinity of the FEF. A frequency power spectrum analysis revealed two predominant frequencies within the functional activation signals from the FEF. One high-intensity signal was present at 0.029 Hz, centering around the block design frequency. The peak-intensity signal was observed between 0.012 and 0.018 Hz where this very low-frequency oscillation (VLFO) was hypothesized to be generated by the macrovasculature present near the FEF and should be avoided as a block design frequency in future fNIRS studies to avoid false positive results.

Resting-state brain activity predicts selective attention deficits during hyperthermia exposure

Purpose Environmental hyperthermia exerts detrimental effect on attention performance that might increase the probability of accidents for high risk occupation. Previously, we reported aberrant activations and selective attention deficits under task performing during hyperthermia. However, whether resting-state baseline during hyperthermia would contribute to the reported selective attention deficits remains unclear. Materials and methods Here, we investigated the resting-state activity within two attention subsystems named dorsal attention network (DAN) and ventral attention network (VAN) using the conjoint analysis of functional connectivity (FC) and regional cerebral blood flow (CBF). Blood oxygenation level dependent (BOLD) and 3 D arterial spin labeling data were obtained from 25 healthy male participants under two simulated thermal conditions: normothermic (25 °C for 1 h) and hyperthermic condition (50 °C for 1 h). Results Paired comparisons on the FC and CBF showed decreased activity in the bilateral frontal eye field (FEF) and intraparietal sulcus (IPS) in the DAN but increased activity in the ventral frontal cortex (VFC) in the VAN. The CBF-FC correlation analysis further confirmed decreased CBF-FC coupling in the bilateral FEF in the DAN and increased coupling in the VFC in the VAN. Additionally, the left IPS and FEF in the DAN showed altered CBF per unit functional connectivity in the CBF/FC ratio analysis. Multiple regression analysis revealed that the selectively altered performances were predicted by alterations of the multiple metrics within the DAN and VAN. Conclusions These findings suggested that altered resting-state brain activity within the attention networks might provide potential neural basis of the selective deficits for different cognitive-demand attention tasks under hyperthermia.

From Prior Information to Saccade Selection: Evolution of Frontal Eye Field Activity during Natural Scene Search.

Prior knowledge about our environment influences our actions. How does this knowledge evolve into a final action plan and how does the brain represent this? Here, we investigated this question in the monkey oculomotor system during self-guided search of natural scenes. In the frontal eye field (FEF), we found a subset of neurons, "Early neurons," that contain information about the upcoming saccade long before it is executed, often before the previous saccade had even ended. Crucially, much of this early information did not relate to the actual saccade that would eventually be selected. Rather, it related to prior information about the probabilities of possible upcoming saccades based on the presaccade fixation location. Nearer to the time of saccade onset, a greater proportion of these neurons' activities related to the saccade selection, although prior information continued to influence activity throughout. A separate subset of FEF neurons, "Late neurons," only represented the final action plan near saccade onset and not prior information. Our results demonstrate how, across the population of FEF neurons, prior information evolves into definitive saccade plans.

Continuous and discrete representations of feature-based attentional priority in human frontoparietal network

ABSTRACTPrevious studies suggest that human frontoparietal network represents feature-based attentional priority, yet the precise nature of the priority signals remains unclear. Here, we examined whether priority signals vary continuously or discretely as a function of feature similarity. In an fMRI experiment, we presented two superimposed dot fields moving along two linear directions (leftward and rightward) while varying the angular separation between the two directions. Subjects were cued to attend to one of the two dot fields and respond to a possible speed-up in the cued direction. We used multivariate analysis to evaluate how priority representation of the attended direction changes with feature similarity. We found that in early visual areas as well as posterior intraparietal sulcus and inferior frontal junction, the patterns of neural activity became more different as the feature similarity decreased, indicating a continuous representation of the attended feature. In contrast, patterns of neural activity in anterior intraparietal sulcus and frontal eye field remained invariant to changes in feature similarity, indicating a discrete representation of the attended feature. Such distinct neural coding of attentional priority across the frontoparietal network may make complementary contributions to enable flexible attentional control.

Characterizing and decomposing the neural correlates of individual differences in reading ability among adolescents with task-based fMRI

To better characterize the neural correlates of the full spectrum of reading ability, this fMRI study examined how variations in reading ability correlate with task-based brain activity during reading among a large community sample of adolescents (N = 234). In addition, complimentary approaches taking advantage of empirical as well as independent meta-analytic information were employed to isolate neural substrates of domain-general executive processes that are predictive of reading ability. Age-related differences in brain activity were also examined. Better reading was associated with increased activation in left anterior and inferior temporal regions and parts of orbitofrontal cortex, along with reduced activation in the thalamus and left frontal eye field (FEF). Converging evidence suggests that FEF activity corresponds to executive processes during reading. In contrast, activity in temporal regions is likely to reflect cognitive processes specific to reading. Older adolescents also demonstrated increased activation in an orbitofrontal region that overlaps with the aforementioned age-independent, reading-related regions, along with reduced activity in parietal and occipital regions. These results suggest that comparedto poor readers, proficient readers benefit from efficient reading-specific processes and require less executive effort, implemented via the FEF, during a reading comprehension task.