Ingrid R. Olson

The parietal cortex and episodic memory: an attentional account.

The contribution of the parietal cortex to episodic memory is a fascinating scientific puzzle. On the one hand, parietal lesions do not normally yield severe episodic-memory deficits; on the other hand, parietal activations are seen frequently in functional-neuroimaging studies of episodic memory. A review of these two categories of evidence suggests that the answer to the puzzle requires us to distinguish between the contributions of dorsal and ventral parietal regions and between the influence of top-down and bottom-up attention on memory.

Amygdala Hyperreactivity in Borderline Personality Disorder: Implications for Emotional Dysregulation.

BACKGROUND Disturbed interpersonal relations and emotional dysregulation are fundamental aspects of borderline personality disorder (BPD). The amygdala plays important roles in modulating vigilance and generating negative emotional states and is often abnormally reactive in disorders of mood and emotion. The aim of this study was to assess amygdala reactivity in BPD patients relative to normal control subjects. We hypothesized that amygdala hyperreactivity contributes to hypervigilance, emotional dysregulation, and disturbed interpersonal relations in BPD. METHODS Using functional magnetic resonance imaging, we examined neural responses to 20-sec blocks of neutral, happy, sad, and fearful facial expression (or a fixation point) in 15 BPD and 15 normal control subjects. The DSM IV-diagnosed BPD patients and the normal control subjects were assessed by a clinical research team in a medical school psychiatry department. RESULTS Borderline patients showed significantly greater left amygdala activation to the facial expressions of emotion (vs. a fixation point) compared with normal control subjects. Post-scan debriefing revealed that some borderline patients had difficulty disambiguating neutral faces or found them threatening. CONCLUSIONS Pictures of human emotional expressions elicit robust differences in amygdala activation levels in borderline patients, compared with normal control subjects, and can be used as probes to study the neuropathophysiologic basis of borderline personality disorder.

Organization of visual short-term memory.

The authors examined the organization of visual short-term memory (VSTM). Using a change-detection task, they reported that VSTM stores relational information between individual items. This relational processing is mediated by the organization of items into spatial configurations. The spatial configuration of visual objects is important for VSTM of spatial locations, colors, and shapes. When color VSTM is compared with location VSTM, spatial configuration plays an integral role because configuration is important for color VSTM, whereas color is not important for location VSTM. The authors also examined the role of attention and found that the formation of configuration is modulated by both top-down and bottom-up attentional factors. In summary, the authors proposed that VSTM stores the relational information of individual visual items on the basis of global spatial configuration.

Working Memory for Conjunctions Relies on the Medial Temporal Lobe

A prominent theory of hippocampal function proposes that the hippocampus is importantly involved in relating or binding together separate pieces of information to form an episodic representation. This hypothesis has only been applied to studies of long-term memory because the paradigmatic view of the hippocampus is that it is not critical for short-term forms of memory. However, relational processing is important in many working memory tasks, especially tasks using visual stimuli. Here, we test the hypothesis that the medial temporal lobes are important for relational memory even over short delays. The task required patients with medial temporal lobe amnesia and controls to remember three objects, locations, or object-location conjunctions over 1 or 8 s delays. The results show that working memory for objects and locations was at normal levels, but that memory for conjunctions was severely impaired at 8 s delays. Additional analyses suggest that the hippocampus per se is critical for accurate conjunction working memory. We propose that the hippocampus is critically involved in memory for conjunctions at both short and long delays.

Dissecting the uncinate fasciculus: disorders, controversies and a hypothesis

The uncinate fasciculus is a bidirectional, long-range white matter tract that connects lateral orbitofrontal cortex and Brodmann area 10 with the anterior temporal lobes. Although abnormalities in the uncinate fasciculus have been associated with several psychiatric disorders and previous studies suggest it plays a putative role in episodic memory, language and social emotional processing, its exact function is not well understood. In this review we summarize what is currently known about the anatomy of the uncinate, we review its role in psychiatric and neurological illnesses, and we evaluate evidence related to its putative functions. We propose that an overarching role of the uncinate fasciculus is to allow temporal lobe-based mnemonic associations (e.g. an individuals name + face + voice) to modify behaviour through interactions with the lateral orbitofrontal cortex, which provides valence-based biasing of decisions. The bidirectionality of the uncinate fasciculus information flow allows orbital frontal cortex-based reward and punishment history to rapidly modulate temporal lobe-based mnemonic representations. According to this view, disruption of the uncinate may cause problems in the expression of memory to guide decisions and in the acquisition of certain types of learning and memory. Moreover, uncinate perturbation should cause problems that extend beyond memory to include social-emotional problems owing to people and objects being stripped of personal value and emotional history and lacking in higher-level motivational value.

Parietal Lobe and Episodic Memory: Bilateral Damage Causes Impaired Free Recall of Autobiographical Memory

Does the parietal lobe have a critical role in memory? The neuroimaging literature indicates that it has an important role, especially in episodic memory. However, the neuropsychological literature suggests that its role is more limited to attentional, spatial, or imagery aspects of memory. Here, we present data to adjudicate this disagreement. Two patients with bilateral parietal lobe damage received detailed assessments of their autobiographical memories. The results show that although both patients easily recalled various memories, their freely recalled memories were relatively impoverished, lacking in detail. This deficit was ubiquitous, and not limited to spatial or perceptual aspects of memory. The memory deficit disappeared when memory was specifically probed by asking pointed questions. Additional tests show that it is unlikely that their free recall deficit can be explained by general mental imagery problems. In sum, the parietal lobe appears to have a critical role in recollection aspects of episodic memory.

Facial attractiveness is appraised in a glance.

Those who are physically attractive reap many benefits--from higher average wages to a wider variety of mate choices. Recent studies have investigated what constitutes beauty and how beauty affects explicit social judgments, but little is known about the perceptual or cognitive processing that is affected by aesthetic judgments of faces and why beauty affects our behavior. In this study, the authors show that beauty is perceived when information is minimized by masking or rapid presentation. Perceiving and processing beauty appear to require little attention and to bias subsequent cognitive processes. These facts may make beauty difficult to ignore, possibly leading to its importance in social evaluations.

Visual Working Memory Is Impaired when the Medial Temporal Lobe Is Damaged

The canonical description of the role of the medial temporal lobes (MTLs) in memory is that short-term forms of memory (e.g., working memory [WM]) are spared when the MTL is damaged, but longer term forms of memory are impaired. Tests used to assess this have typically had a heavy verbal component, potentially allowing explicit rehearsal strategies to maintain the WM trace over the memory delay period. Here we test the hypothesis that the MTL is necessary for visual WM when verbal rehearsal strategies are difficult to implement. In three patients with MTL damage we found impairments in spatial, face, and color WM, at delays as short as 4 sec. Impaired memory could not be attributed to memory load or perceptual problems. These findings suggest that the MTLs are critical for accurate visual WM.

Perceptual constraints on implicit learning of spatial context

Invariant spatial relationships of objects may provide a rich source of contextual information. Visual context can assist localization of individual objects via an implicit learning mechanism, as revealed in the contextual cueing paradigm (Chun & Jiang, 1998). What defines a visual context? How robust is contextual learning? And is it perceptually constrained? Here we investigate whether both local context that surround a target, and long-range context that does not spatially coincide with a target, can influence target localization. In the contextual cueing task, participants implicitly learned a context by repeated exposure to items arranged in invariant patterns. Experiments 1 and 2 suggest that only local context facilitates target localization. However, Experiment 3 showed that long range context can prime target location when target and context are not separated by random information. Experiment 4 showed that grouping by colour does not affect contextual cueing, suggesting that spatial features play a more important role than surface features in spatial contextual cueing. In separate analyses, visual hemifield differences were found for learning and performance. In sum, the results indicate that implicit learning of spatial context is robust across noise and biased towards spatially grouped information.

Is visual short-term memory object based? Rejection of the " strong-object" hypothesis

Is the capacity of visual short-term memory (VSTM) limited by the number of objects or by the number of features? VSTM for objects with either one feature or two color features was tested. Results show that capacity was limited primarily by the number of colors to be memorized, not by the number of objects. This result held up with variations in color saturation, blocked or mixed conditions, duration of memory image, and absence or presence of verbal load. However, conjoining features into objects improved VSTM capacity when size-orientation and color-orientation conjunctions were tested. Nevertheless, the number of features still mattered. When feature heterogeneity was controlled, VSTM for conjoined objects was worse than VSTM for objects made of single features. Our results support a weak-object hypothesis of VSTM capacity that suggests that VSTM is limited by both the number of objects and the feature composition of those objects.