A common neural system mediating two different forms of social judgement.

BACKGROUND: A wide range of neuropsychiatric conditions, including schizophrenia and autistic spectrum disorder (ASD), are associated with impairments in social function. Previous studies have shown that individuals with schizophrenia and ASD have deficits in making a wide range of social judgements from faces, including decisions related to threat (such as judgements of approachability) and decisions not related to physical threat (such as judgements of intelligence). We have investigated healthy control participants to see whether there is a common neural system activated during such social decisions, on the basis that deficits in this system may contribute to the impairments seen in these disorders. METHOD: We investigated the neural basis of social decision making during judgements of approachability and intelligence from faces in 24 healthy participants using functional magnetic resonance imaging (fMRI). We used conjunction analysis to identify common brain regions activated during both tasks. RESULTS: Activation of the amygdala, medial prefrontal cortex, inferior prefrontal cortex and cerebellum was seen during performance of both social tasks, compared to simple gender judgements from the same stimuli. Task-specific activations were present in the dorsolateral prefrontal cortex in the intelligence task and in the inferior and middle temporal cortex in the approachability task. CONCLUSIONS: The present study identified a common network of brain regions activated during the performance of two different forms of social judgement from faces. Dysfunction of this network is likely to contribute to the broad-ranging deficits in social function seen in psychiatric disorders such as schizophrenia and ASD.

Dissociating memory retrieval processes using fMRI: evidence that priming does not support recognition memory.

We employed event-related fMRI to constrain cognitive accounts of memory retrieval. Studies of explicit retrieval reveal that lateral and medial parietal, dorsal middle frontal gyrus, and anterior prefrontal cortex respond more for studied than new words, reflecting a correlate of "retrieval success." Studies of implicit memory suggest left temporal cortex, ventral and dorsal inferior frontal gyrus respond less for studied than new words, reflecting a correlate of "conceptual priming." In the present study, responses for old and new items were compared during performance on explicit recognition (old/new judgement) and semantic (abstract/concrete judgement) tasks. Regions associated with priming were only modulated during the semantic task, whereas regions associated with retrieval success were modulated during both tasks. These findings constrain functional-anatomic accounts of the networks, suggesting that processes associated with priming do not support explicit recognition judgments.

Human brain activity time-locked to perceptual event boundaries.

Temporal structure has a major role in human understanding of everyday events. Observers are able to segment ongoing activity into temporal parts and sub-parts that are reliable, meaningful and correlated with ecologically relevant features of the action. Here we present evidence that a network of brain regions is tuned to perceptually salient event boundaries, both during intentional event segmentation and during naive passive viewing of events. Activity within this network may provide a basis for parsing the temporally evolving environment into meaningful units.

Transient activation during block transition.

Functional MRI (fMRI) data analysis of blocked-task paradigms typically considers brain activity present across a temporally extended task block relative to a reference block. An open question remains as to whether processes evolving with distinct temporal profiles are also present and can inform us about further functional-anatomic processes underlying task performance. To explore this question, a meta-analysis of data from these separate studies was performed. The meta-analysis specifically focused on detecting transient activation occurring at the onset and offset of task blocks. The composite data set from 39 subjects included four distinct task conditions (from various intentional encoding paradigms) that had equivalent block timing. Task block activation included a network of regions consistent with prior analyses of intentional encoding. Activation related to the block transitions included a set of transiently activated regions, consistent across all four separate task conditions. The most prominent activation was found in right frontal cortex along the dorsal extent of inferior frontal gyrus (near BA 6/44). Importantly, in one condition, this transient activation was present in the absence of a response across the task block suggesting dissociation between processes in support of ongoing task demands and those associated with transitions between blocks. Other prominent transient activations included posterior superior temporal sulcus, medial occipitoparietal sulcus, anterior insula, and anterior cingulate sulcus in the right hemisphere. These findings are discussed in relation to models of set shifting and competitive interactions between brain regions.

Dissociating state and item components of recognition memory using fMRI.

Cognitive functions such as memory retrieval involve a combination of state- and item-related processes. State-related processes are sustained throughout a task (e.g., "retrieval mode" associated with ongoing goals), whereas item-related processes are transient and allied to individual stimuli (e.g., "retrieval success" associated with the recovery of information from memory). The present study employed a mixed "blocked and event-related" experimental design to identify neural mechanisms that support state- and item-related processes during a recognition memory task. Subjects alternated between blocks of fixation and recognition memory (discriminating between old and new words). Critically, event-related procedures were embedded within the recognition blocks, including the jittering of sequential trials. This design ensures that the temporal profiles of state- and item-related activity differ and consequently renders them separable; without this procedure item-related activity would summate to produce a state-like response. Results suggest three classes of brain region support recognition memory, exhibiting: (1) predominantly transient activity (including regions in medial parietal, lateral parietal, and anterior left frontal cortex) reflecting item-related processing associated with "retrieval success," (2) predominantly sustained activity (including decreased activity in bilateral parahippocampal cortex) reflecting state-related processing associated with "retrieval mode," (3) concurrent sustained and transient activity (including regions in left middle frontal gyrus, bilateral frontal operculum, and medial frontal gyrus), reflecting a combination of state- and item-related processing. The present findings support the idea that recognition memory tasks are dependent upon a combination of state- and item-related processes that have dissociable neural correlates identifiable using fMRI. Moreover, the mixed "blocked and event-related" design employed here provides a general procedure for separating state- and item-related processes.

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.

Cognitive neuroscience of episodic memory encoding.

This paper presents a cognitive neuroscientific perspective on how human episodic memories are formed. Convergent evidence from multiple brain imaging studies using positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) suggests a role for frontal cortex in episodic memory encoding. Activity levels within frontal cortex can predict episodic memory encoding across a wide range of behavioral manipulations known to influence memory performance, such as those present during levels of processing and divided attention manipulations. Activity levels within specific frontal and medial temporal regions can even predict, on an item by item basis, whether an episodic memory is likely to form. Furthermore, separate frontal regions appear to participate in supplying code-specific information, including distinct regions which process semantic attributes of verbal information as well as right-lateralized regions which process nonverbal information. We hypothesize that activity within these multiple frontal regions provides a functional influence (input) to medical temporal regions that bind the information together into a lasting episodic memory trace.

Event-related potential studies of associative recognition and recall: electrophysiological evidence for context dependent retrieval processes.

To investigate the neural correlates of episodic recollection the ERP correlates of memory for new associations (recently studied novel word pairs) were investigated using two tasks, associative recognition and associative recall. For the recognition task subjects discriminated old from new word pairs and, for pairs judged old, reported whether the pairs were intact or recombined (compared to at study). For the recall task, subjects discriminated old from new words and, for each word judged old, reported its study associate. ERPs were recorded at test from 25 scalp electrodes, with a 1944-ms recording epoch. In Experiment 1, the tasks were randomly interleaved. Consistent with previous findings, relative to the ERPs for correctly classified new items, the ERP correlates of successful associative recognition consisted of a sustained left parietal positivity, and two frontal positivities, one early and bilateral, the other occurring later and showing a right-sided maximum. In contrast to previous findings, successful associative recall elicited similar effects to those found for recognition. Topographic analyses revealed that the distribution of these retrieval-related ERP effects were similar across the two tasks, suggesting that the recognition and recall of associative information gives rise to activity in overlapping, if not the same, neural populations. In Experiment 2 the tasks were blocked. In contrast to the findings of Experiment 1, successful associative recall elicited left parietal and late onsetting right frontal positivities, in the absence of the early bilateral frontal positivity. This finding suggests that frontally-distributed memory-related ERP effects are both neurally and functionally dissociable. Specifically, we argue that the functional significance of the early frontally distributed ERP effect cannot be accounted for by the 'post-retrieval processing' hypothesis that is taken to account for the late right frontal effect, suggesting that episodic recollection itself is neither neurally nor functionally homogenous.

Recognition memory for new associations: electrophysiological evidence for the role of recollection.

The electrophysiological correlates of recognition memory for new associations were investigated in two experiments. In both experiments subjects first studied unrelated word pairs. At test, they were presented with old words in the same pairing as at study (same pairs), old words in a different pairing from study (rearranged pairs), and pairs of new words. In Experiment 1 the test requirement was to discriminate between old and new pairs and, for any pair judged old, to then judge whether the pair was the same or rearranged. In Experiment 2 the requirement was merely to discriminate between old and new pairs. Event-related potentials (ERPs) were recorded for correctly classified same, rearranged and new pairs. The ERPs elicited by same pairs exhibited a similar pattern of effects in both experiments. Relative to the ERPs to new pairs, these effects took the form of sustained positive shifts with two distinct scalp maxima, over the left temporo-parietal and right frontal scalp respectively. ERPs to rearranged pairs showed effects which were similar in scalp topography, but markedly smaller in magnitude. This pattern of ERP effects closely resembles that found previously for test items defined as recollected on the basis of their attracting a successful source judgement. The findings therefore suggest that associative recognition memory shares some of the recollective processes that are engaged by the requirement to retrieve contextual information about a study episode. The findings from Experiment 2 indicate that the processes associated with the recollection of associated pairs are engaged regardless of whether the retrieval of associative information is an explicit task requirement.