Spatial memory encoding is associated with the anterior and posterior hippocampus: An fMRI activation likelihood estimation meta-analysis.

It has been hypothesized that differential processing occurs along the longitudinal (anterior-posterior) axis of the hippocampus. One hypothesis is that spatial memory (during both encoding and retrieval) is associated with the posterior hippocampus. An alternative hypothesis is that memory encoding (either spatial or nonspatial) is associated with the anterior hippocampus and memory retrieval is associated with the posterior hippocampus.

The hippocampus and implicit memory.

The traditional memory-systems view is that explicit (conscious) long-term memory is associated with the hippocampus and implicit (nonconscious) memory is associated with non-hippocampal brain regions. This special issue of focuses on whether the hippocampus is associated with implicit memory. An empirical fMRI paper by Miller, Kennard, Gowland, Antoniades, and Rosenthal (this issue) evaluated recognition memory performance of autobiographical amnesia patients with bilateral damage to hippocampal sub-region CA3 and found they had greater than chance recognition memory performance for spatial sequence learning, spatial item learning-same location, and non-spatial item learning, but chance performance for non-spatial sequence learning and spatial item learning-different location.

True and false memories for spatial location evoke more similar patterns of brain activity in males than females.

True and false memories recruit a number of shared brain regions; however, they are not completely overlapping. Extensive sex differences have been identified in the brain during true memories and, recently, we identified sex differences in the brain during false memories. In the current fMRI study, we sought to determine whether sex differences existed in the location and extent of overlap between true and false memories.

Is implicit memory associated with the hippocampus?

According to the traditional memory-systems view, the hippocampus is critical during explicit (conscious) long-term memory, whereas other brain regions support implicit (nonconscious) memory. In the last two decades, some fMRI studies have reported hippocampal activity during implicit memory tasks. The aim of the present discussion paper was to identify whether any implicit memory fMRI studies have provided convincing evidence that the hippocampus is associated with nonconscious processes without being confounded by conscious processes.

Can Residents With Late-Stage Dementia Still Engage?

Institutionalized persons with dementia often lack access to meaningful activity, which can lead to agitation, loneliness, and depression. Engagement in activity may improve negative symptoms but is difficult in most settings. In this study, we investigated the degree to which the Reading Buddies Program, in which occupational therapy graduate students read books with residents with dementia, engaged residents.

TMS must not harm participants: guidelines for evaluating TMS protocol safety.

Transcranial magnetic stimulation (TMS) can modulate a targeted brain region to assess whether that region is involved in a cognitive process. When TMS is employed in cognitive neuroscience, participants are typically healthy volunteers, and the technique is described as noninvasive. However, TMS parameters can be set such that stimulation produces long-lasting effects.

Prefrontal cortex-mediated inhibition supports face recognition.

Inhibitory processes are thought to be important for memory function. A recent behavioral study that employed a face recognition paradigm reported that participants made fewer "old" responses to highly similar faces than less similar faces, providing evidence that memory for faces may rely on related-item inhibition. However, these results could also be explained by a non-inhibitory recall-to-reject process.

No convincing evidence the hippocampus is associated with working memory.

In a previous discussion paper , twenty-six working memory fMRI studies that reported activity in the hippocampus were systematically analyzed. None of these studies provided convincing evidence that the hippocampus was active during the late delay phase, the only period in which working memory can be isolated from long-term memory processes. Based on these results, it was concluded that working memory does not activate the hippocampus.

Entorhinal Cortex Functional Connectivity during Item Long-Term Memory and the Role of Sex.

A growing body of literature shows there are sex differences in the patterns of brain activity during long-term memory. However, there is a paucity of evidence on sex differences in functional brain connectivity. We previously identified sex differences in the patterns of connections with the hippocampus, a medial temporal lobe (MTL) subregion, during spatial long-term memory.

Impaired cognitive performance in older adults is associated with deficits in item memory and memory for object features.

Amnestic mild cognitive impairment (aMCI) is associated with damage to the perirhinal/entorhinal cortex, and consequently, deficits in item/object memory. However, cognitive assessments commonly used to identify individuals with aMCI require a clinician to administer and interpret the test. We developed a novel self-administered global cognitive assessment, called the Cognitive Assessment via Keyboard (CAKe).

Sex is predicted by spatial memory multivariate activation patterns.

Whether sex differences exist in the brain at the macroscopic level, as measured with magnetic resonance imaging (MRI), is a topic of debate. The present spatial long-term memory functional MRI (fMRI) study predicted sex based on event-related patterns of brain activity. Within spatial memory regions of interest, patterns of activity associated with females and males were used to predict the sex of each member of left-out female-male pairs at above-chance accuracy.

The hippocampus and long-term memory.

This special issue of focuses on the roles of the hippocampus during long-term memory. A discussion paper by Tallman, Clark, and Smith (this issue) found that functional connectivity of the hippocampus with the parahippocampal cortex and fusiform gyrus decreased with memory age, providing support for systems consolidation. Commentaries were received by Berdugo-Vega and Gräff (this issue), Feld and Gerchen (this issue), Gellersen and Simons (this issue), Gobbo, Mitchell-Heggs, and Tse (this issue), Gilmore, Audrain, and Martin (this issue), Kirwan (this issue), Manns (this issue), Runyan and Brooks (this issue), Santangelo (this issue), and Yang (this issue).

Does working memory activate the hippocampus during the late delay period?

The aim of the present discussion paper was to identify whether any fMRI studies have provided convincing evidence that the hippocampus is associated with working memory. The key outcome variable was the phase in which hippocampal activity was observed: study, early delay, late delay, and/or test. During working memory tasks, long-term memory processes can operate during the study phase, early delay phase (due to extended encoding), or test phase.

It's time for sex in cognitive neuroscience.

In a discussion paper published in the special issue of , Sex Differences in the Brain, we investigated whether certain experimental parameters contributed to findings in functional magnetic resonance imaging studies of sex differences during long-term memory. Experimental parameters included: the number of participants, stimulus type(s), whether or not performance was matched, whether or not sex differences were reported, the type of between-subject statistical test used, and the contrast(s) employed. None of these parameters determined whether or not differences were observed, as all included studies reported sex differences.

Sex differences in the brain.

This special issue of focuses on sex differences in the brain. Berchicci, Bianco, and Di Russo found ERP auditory cortex activity was larger in females than males during sound perception. Spets, Fritch, Thakral, & Slotnick reported greater fMRI activity during high- versus low-confidence spatial memory in males than females within the lateral prefrontal cortex and other brain regions.

Distinct patterns of hippocampal activity associated with color and spatial source memory.

The hippocampus is known to be involved in source memory across a wide variety of stimuli and source types. Thus, source memory activity in the hippocampus is thought to be domain-general such that different types of source information are similarly processed in the hippocampus. However, there is some evidence of domain-specificity for spatial and temporal source information.

Support for an inhibitory model of word retrieval.

Word retrieval may involve an inhibitory process in which a target word is activated and related words are suppressed. In the current functional magnetic resonance imaging (fMRI) study, we examined the inhibition of language processing cortex by the left dorsolateral prefrontal cortex (DLPFC) during word retrieval using an anagram-solving paradigm. Participants were presented with a distractor that was read aloud followed by a to-be-solved anagram.

Sex differences in hippocampal connectivity during spatial long-term memory.

Sex differences in brain activity have been reported across various types of long-term memory. To our knowledge, sex differences in functional connectivity during long-term memory have not been investigated. A previous study on the structural connectome identified that female brains have a greater degree of interhemispheric connectivity than males, whereas males have a greater degree of intrahemispheric connectivity than females.

Thalamic Functional Connectivity during Spatial Long-Term Memory and the Role of Sex.

The thalamus has been implicated in many cognitive processes, including long-term memory. More specifically, the anterior (AT) and mediodorsal (MD) thalamic nuclei have been associated with long-term memory. Despite extensive mapping of the anatomical connections between these nuclei and other brain regions, little is known regarding their functional connectivity during long-term memory.

Functional connectivity with the anterior and posterior hippocampus during spatial memory.

Evidence of differential connectivity and activity patterns across the long-axis of the hippocampus has led to many hypotheses about functional specialization of the anterior and posterior hippocampus, including a hypothesis linking the anterior hippocampus to memory encoding and the posterior hippocampus to memory retrieval. The hippocampal encoding/retrieval and network (HERNET) model of memory predicts that encoding should engage the anterior hippocampus and the attention network, whereas retrieval should engage the posterior hippocampus and the default network. In a previous fMRI study that employed multivoxel pattern analysis, we found that the patterns of activity in the anterior hippocampus predicted the quadrant of spatial memory encoding.

High confidence spatial long-term memories produce greater cortical activity in males than females.

Many functional resonance imaging (fMRI) studies have reported sex differences during long-term memory. The present fMRI investigation aimed to identify whether sex differences exist during high- versus low-confidence accurate spatial memories. During the study phase, abstract shapes were presented to the left or right of fixation.

Are there sex differences in brain activity during long-term memory? A systematic review and fMRI activation likelihood estimation meta-analysis.

The degree to which sex differences exist in the brain is a current topic of debate. In the present discussion paper, we reviewed eight functional magnetic resonance imaging (fMRI) papers to determine whether there are sex differences in brain activity during long-term memory retrieval. The objectives were: 1) to compare the experimental parameters in studies reporting significant versus null long-term memory sex differences, and 2) to identify whether specific brain regions were associated with sex differences during long-term memory.

The anterior hippocampus is associated with spatial memory encoding.

There are many hypotheses regarding specialization of the anterior versus posterior hippocampus including memory encoding versus retrieval and other cognitive processes versus spatial memory. In the present functional magnetic resonance imaging study, we distinguished between the hypothesis linking encoding to the anterior hippocampus and the hypothesis linking spatial memory to the posterior hippocampus by evaluating whether spatial memory encoding involved the anterior hippocampus or the posterior hippocampus. During encoding, participants viewed abstract shapes in each of four visual field quadrants while instructed to maintain central fixation.

Long-term memory specificity depends on inhibition of related items.

Long-term memory relies on both accurately retrieving specific details and inhibiting competing information. In the current investigation, we evaluated the specificity of long-term memory representations for faces. During each study phase, participants were presented with neutral Caucasian male and female faces.

Forgotten but not gone: FMRI evidence of implicit memory for negative stimuli 24 hours after the initial study episode.

Endel Tulving conducted pioneering work on the explicit and implicit memory systems and demonstrated that priming effects can be long-lasting. It is also well-established that emotion can amplify explicit and implicit memory. Prior work has utilized repetition suppression (RS) of the fMRI-BOLD signal-a reduction in the magnitude of activity over repeated presentations of stimuli-to index implicit memory.