Temporally Graded Activation of Neocortical Regions in Response to Memories of Different Ages

The temporally graded memory impairment seen in many neurobehavioral disorders implies different neuroanatomical pathways and/or cognitive mechanisms involved in storage and retrieval of memories of different ages. A dynamic interaction between medial-temporal and neocortical brain regions has been proposed to account for memory\u27s greater permanence with time. Despite considerable debate concerning its time-dependent role in memory retrieval, medial-temporal lobe activity has been well studied. However, the relative participation of neocortical regions in recent and remote memory retrieval has received much less attention. Using functional magnetic resonance imaging, we demonstrate robust, temporally graded signal differences in posterior cingulate, right middle frontal, right fusiform, and left middle temporal regions in healthy older adults during famous name identification from two disparate time epochs. Importantly, no neocortical regions demonstrated greater response to older than to recent stimuli. Our results suggest a possible role of these neocortical regions in temporally dating items in memory and in establishing and maintaining memory traces throughout the lifespan. Theoretical implications of these findings for the two dominant models of remote memory functioning (Consolidation Theory and Multiple Trace Theory) are discussed

Memory and law: what can cognitive neuroscience contribute?

A recent decision in the United States by the New Jersey Supreme Court has led to improved jury instructions that incorporate psychological research showing that memory does not operate like a video recording. Here we consider how cognitive neuroscience could contribute to addressing memory in the courtroom. We discuss conditions in which neuroimaging can distinguish true and false memories in the laboratory and note reasons to be skeptical about its use in courtroom cases. We also discuss neuroscience research concerning false and imagined memories, misinformation effects and reconsolidation phenomena that may enhance understanding of why memory does not operate like a video recording.Psycholog

HIT and brain reward function: a case of mistaken identity (theory)

This paper employs a case study from the history of neuroscience—brain reward function—to scrutinize the inductive argument for the so-called ‘Heuristic Identity Theory’ (HIT). The case fails to support HIT, illustrating why other case studies previously thought to provide empirical support for HIT also fold under scrutiny. After distinguishing two different ways of understanding the types of identity claims presupposed by HIT and considering other conceptual problems, we conclude that HIT is not an alternative to the traditional identity theory so much as a relabeling of previously discussed strategies for mechanistic discovery

Remembering verbally-presented items as pictures:brain activity underlying visual mental images in schizophrenia patients with visual hallucinations

Background: Previous research suggests that visual hallucinations in schizophrenia consist of mental images mistaken for percepts due to failure of the reality-monitoring processes. However, the neural substrates that underpin such dysfunction are currently unknown. We conducted a brain imaging study to investigate the role of visual mental imagery in visual hallucinations. Method: Twenty-three patients with schizophrenia and 26 healthy participants were administered a reality-monitoring task whilst undergoing an fMRI protocol. At the encoding phase, a mixture of pictures of common items and labels designating common items were presented. On the memory test, participants were requested to remember whether a picture of the item had been presented or merely its label. Results: Visual hallucination scores were associated with a liberal response bias reflecting propensity to erroneously remember pictures of the items that had in fact been presented as words. At encoding, patients with visual hallucinations differentially activated the right fusiform gyrus when processing the words they later remembered as pictures, which suggests the formation of visual mental images. On the memory test, the whole patient group activated the anterior cingulate and medial superior frontal gyrus when falsely remembering pictures. However, no differential activation was observed in patients with visual hallucinations, whereas in the healthy sample, the production of visual mental images at encoding led to greater activation of a fronto-parietal decisional network on the memory test. Conclusions: Visual hallucinations are associated with enhanced visual imagery and possibly with a failure of the reality-monitoring processes that enable discrimination between imagined and perceived events

Cortical Thickness Abnormalities Within the Salience and Reward Networks in Older Depressed Adults with Apathy

Background and Significance: Apathy is a common comorbidity in late-life depression. Among older depressed adults, apathy is associated with a number of adverse outcomes, including increased disability, comorbid illness, and mortality. The etiological substrates of apathy in late-life depression nonetheless remain poorly understood, and little is known about its optimal treatment. To this end, the aim of the current study was to examine cortical abnormalities within the salience (SN) and reward networks (RN), two brain systems involved in the processing of incentive salience that may underlie the syndrome of apathy in older depressed adults. Methods: We examined the association between apathy and cortical thickness of the right insula, caudal anterior cingulate cortex (cACC), rostral anterior cingulate cortex (rACC), medial orbitofrontal cortex (mOFC), and lateral orbitofrontal cortex (lOFC) in 49 individuals with late-life depression before and after 12 weeks of antidepressant treatment with the selective serotonin reuptake inhibitor (SSRI) escitalopram. Apathy was quantified using the Apathy Evaluation Scale (AES). Cortical thickness was computed using FreeSurfer. Regions of interest (ROIs) were parcellated using the Desikan-Killiany atlas. Results: Within the SN, cortical thickness of the insula was significantly associated with response of apathy symptoms to escitalopram, as well as persistence of apathy symptoms after 12 weeks of treatment. Thickness of the cACC, which is involved in both salience and reward processing, was not associated with apathy at any time. Within the RN, thickness of the rACC was significantly related to apathy at baseline. Thickness of the mOFC and lOFC was not associated with apathy at any time. Exploratory analyses examining the association between cognitive functions and apathy revealed a relationship between response of apathy to treatment and several aspects of cognition, including processing speed, executive functioning (i.e., set shifting and source monitoring), and memory (i.e., retrieval of verbal information). Conclusions: The results of this study suggest a role for abnormalities within both the SN and RN in older depressed adults with apathy. Given the interplay between structures of the SN and RN in processing of incentive salience, older depressed adults with apathy may have a decreased ability to associate an anticipated outcome with the experience of desire, thereby decreasing motivated, goal-directed activity

Constructive memory: past and future

Human memory is not a literal reproduction of the past, but instead relies on constructive processes that are sometimes prone to error and distortion. Understanding of constructive memory has accelerated during recent years as a result of research that has linked together its cognitive and neural bases. This article focuses on three aspects of constructive memory that have been the target of recent research: (i) the idea that certain kinds of memory distortions reflect the operation of adaptive cognitive processes that contribute to the efficient functioning of memory; (ii) the role of a constructive memory system in imagining or simulating possible future events; and (iii) differences between true and false memories that have been revealed by functional neuroimaging techniques. The article delineates the theoretical implications of relevant research, and also considers some clinical and applied implications

Time to Go Our Separate Ways: Opposite Effects of Study Duration on Priming and Recognition Reveal Distinct Neural Substrates

Amnesic patients have difficulties recognizing when stimuli are repeated, even though their responses to stimuli can change as a function of repetition in indirect tests of memory – a pattern known as priming without recognition. Likewise, experimental manipulations can impair recognition in healthy individuals while leaving priming relatively unaffected, and priming and recognition have been associated with distinct neural correlates in these circumstances. Does this evidence necessarily indicate that priming and recognition rely on distinct brain systems? An alternative explanation is that recognition is merely more sensitive to amnestic insults and experimental manipulations than is priming, and that both priming and recognition are produced by a single brain system. If so, then experimental manipulations would tend to drive priming and recognition in the same direction, albeit to a greater extent for one versus the other in some circumstances. We found evidence to the contrary – that manipulating study duration has opposite effects on priming versus recognition. Studying objects for one-quarter second led to worse recognition than studying objects for 2 s, whereas the opposite was true for priming (greater for one-quarter-second study than two-second study). Furthermore, distinct electrophysiological repetition effects were associated with priming versus recognition. We therefore conclude that study duration had opposite effects on priming and recognition, and on the engagement of implicit versus explicit memory systems. These findings call into question single-process accounts of priming and recognition, and substantiate previous behavioral, neuropsychological, and neuroimaging dissociations between implicit and explicit memory

A Common Anterior Insula Representation of Disgust Observation, Experience and Imagination Shows Divergent Functional Connectivity Pathways

Similar brain regions are involved when we imagine, observe and execute an action. Is the same true for emotions? Here, the same subjects were scanned while they (a) experience, (b) view someone else experiencing and (c) imagine experiencing gustatory emotions (through script-driven imagery). Capitalizing on the fact that disgust is repeatedly inducible within the scanner environment, we scanned the same participants while they (a) view actors taste the content of a cup and look disgusted (b) tasted unpleasant bitter liquids to induce disgust, and (c) read and imagine scenarios involving disgust and their neutral counterparts. To reduce habituation, we inter-mixed trials of positive emotions in all three scanning experiments. We found voxels in the anterior Insula and adjacent frontal operculum to be involved in all three modalities of disgust, suggesting that simulation in the context of social perception and mental imagery of disgust share a common neural substrates. Using effective connectivity, this shared region however was found to be embedded in distinct functional circuits during the three modalities, suggesting why observing, imagining and experiencing an emotion feels so different