Palva S, Palva JM.
Article in Trends in Neurosciences

Abstract
The amplitude of alpha-frequency band (8-14 Hz) activity in the human electroencephalogram is suppressed by eye opening, visual stimuli and visual scanning, whereas it is enhanced during internal tasks, such as mental calculation and working memory. Alpha-frequency band oscillations have hence been thought to reflect idling or inhibition of task-irrelevant cortical areas. However, recent data on alpha-amplitude and, in particular, alpha-phase dynamics posit a direct and active role for alpha-frequency band rhythmicity in the mechanisms of attention and consciousness. We propose that simultaneous alpha-, beta- (14-30 Hz) and gamma- (30-70 Hz) frequency band oscillations are required for unified cognitive operations, and hypothesize that cross-frequency phase synchrony between alpha, beta and gamma oscillations coordinates the selection and maintenance of neuronal object representations during working memory, perception and consciousness.

Read more... Comments (0)

In a past study, Klimesch and colleagues examined whether the conscious experience of remembering and knowing are associated with neural synchronization in the theta bandwidth.  These investigators first presented participants with a series of words (through both auditory and visual means) and then tested participants’ memory for these words using a recognition test and the “Remember-Know” task. 

During the recognition test, participants were shown a series of words (the participants saw some of these words earlier during the experiment, whereas other words were not seen before) and were asked to judge whether these same words were presented to them earlier.  For those words that were judged as “old” (previously presented), participants also performed the Remember-Know task. 

The Remember-Know task is widely used in memory research to study one’s state of consciousness during a recognition decision.  ”Remember” judgments are made when an “old” decision on the recognition test is accompanied by awareness of details of the previous occurrence of the stimulus in question.  “Know” judgments are made when an “old” decision is not accompanied by such awareness.

Among other interesting results, Klimesch and colleagues found that theta power was larger for Know judgments early during the recognition period of a word (300 – 450 ms) and larger for Remember judgments during a later period (450 – 625 ms). The investigators concluded that these patterns of theta associated with Remember and Know judgments demonstrate that the temporal dynamics of the neural synchronization plays an important role in the experiential characteristics associated with memory retrieval.

Read more... Comments (0)

The feeling of familiarity can be triggered by stimuli from all sensory modalities, suggesting a multimodal nature of its neural bases.

In the present experiment, we investigated this hypothesis by studying the neural bases of familiarity processing of odors and music. In particular, we focused on familiarity referring to the participants’ life experience. Items were classified as familiar or unfamiliar based on participants’ individual responses, and activation patterns evoked by familiar items were compared with those evoked by unfamiliar items. For the feeling of familiarity, a bimodal activation pattern was observed in the left hemisphere, specifically the superior and inferior frontal gyri, the precuneus, the angular gyrus, the parahippocampal gyrus, and the hippocampus.

Together with previously reported data on verbal items, visual items, and auditory items other than music, this outcome suggests a multimodal neural system of the feeling of familiarity. The feeling of unfamiliarity was related to a smaller bimodal activation pattern mainly located in the right insula and likely related to the detection of novelty.

Plailly et al. in Cerebral Cortex

Read more... Comments (4)

Familiarity is a pervasive memory phenomenon that occurs in its most basic form when someone recognizes a repeated stimulus without recollecting other aspects of the requisite prior learning episode. Theoretical controversy currently abounds with respect to both the cognitive and neural characteristics of familiarity. Here, we show that the extant data, particularly brain-potential data, are insufficient for validating putative neural correlates of familiarity, and we outline strategies for making progress on this problem. Conceptual priming is an implicit-memory phenomenon that often occurs together with familiarity; experiments that conflate the two phenomena can be misleading. Avoiding this conflation is required to understand familiarity and to determine the extent to which the neurocognitive processes that support priming also drive familiarity.

Hubmed

Paller KA, Voss JL, Boehm SG
Trends Cogn Sci. 2007 Jun ; 11(6): 243-50

Read more... Comments (2)

Declarative memories — memories for facts and events in time — become more resistant to interference during sleep, according to a study that will presented at the 59th Annual Meeting of the American Academy of Neurology (AAN) in Boston, Massachusetts.

“We know that sleep helps boost memory for procedural tasks, such as learning a new piano sequence. But we’re not sure, even though it’s been debated for over a hundred years, whether sleep impacts declarative memory,” said lead author Jeffrey Ellenbogen, MD, a clinical fellow in medicine at Harvard Medical School, in Boston.

Read more... Comments (1)

TIME and CNN present an interesting video on Sarah Scantlin, a patient who suffers from severe brain damage. After being stuck in what was thought to be a vegetative state for 20 years, Sarah has recently regained her ability to speak. Scientists now think that Sarah was in a minimally conscious state, described as having a low level of awareness but conscious nonetheless, for the past two decades. It is noted that while some regions of Sarah’s brain are damaged, other regions are struggling to make new connections. (Image from the video.)

When asked whether she felt asleep or trapped for the last 20 years, Sarah reported having felt trapped. Amongst other challenges, Sarah seems to lack a concept of time, leaving her to believe that she is still 18 (the age at which she incurred her brain injury) when in fact she is now at the age of 40 years.

Read more... Comments (0)

Abstract of Self-projection and the brain, in Trends in Cognitive Science:

When thinking about the future or the upcoming actions of another person, we mentally project ourselves into that alternative situation. Accumulating data suggest that envisioning the future (prospection), remembering the past, conceiving the viewpoint of others (theory of mind) and possibly some forms of navigation reflect the workings of the same core brain network. These abilities emerge at a similar age and share a common functional anatomy that includes frontal and medial temporal systems that are traditionally associated with planning, episodic memory and default (passive) cognitive states. We speculate that these abilities, most often studied as distinct, rely on a common set of processes by which past experiences are used adaptively to imagine perspectives and events beyond those that emerge from the immediate environment.

Read more... Comments (1)

Can birds remember who watched them do what, as well as when and where?

Scrub jays have already been demonstrated to encode the “what-where-when” (what happened, where it happened and when it happened) of specific caching episodes (Clayton, N.S. & Dickenson, A., 1998). It has even been shown that scrub jays, when observed caching food, re-cache food only if they have stolen the food of another bird in the past (Emery & Clayton, 2001). This finding suggests that jays who have stolen food in the past can also anticipate their own food being stolen in the future, and, therefore, take precautionary measures to reduce this possibility.

Now, the results of a recent study by Dally et al. (2006) suggest that scrub jays also remember who was present during earlier caching events. In this study, jays were more likely to re-cache food if a more dominant bird observed them caching than if a less dominant bird did so. As Dally et al. note, since scrub-jays can only defend their caches against subordinates, it seems very likely that the observed re-caching behaviour is advantageous in situations where the jays are caching in view of dominant birds, as it is thought to reduce the likelihood of future pilfering.

Read more... Comments (0)

Are memory errors really a bad thing? Could they actually reflect processes that are adaptive for our existence? Schacter and Addis discuss this interesting idea in an essay on constructive memory. (Continue reading for a passage from the essay.)

Read more... Comments (0)

Issues in Philosophy and Psychology (Consciousness and Self-Consciousness Series, 1)
by Christoph Hoerl (Editor), Teresa McCormack (Editor)

The capacity to represent and think about time is one of the most fundamental and least understood aspects of human cognition and consciousness. This book throws new light on central issues in the study of the mind by uniting, for the first time, psychological and philosophical approaches dealing with the connection between temporal representation and memory. Fifteen specially written essays by leading psychologists and philosophers investigate the way in which time is represented in memory, and the role memory plays in our ability to reason about time. They offer insights into current theories of memory processes and of the mechanisms and cognitive abilities underlying temporal judgments, and draw out fundamental issues concerning the phenomenology and epistemology of memory and our understanding of time. The chapters are arranged into four sections, each focused on one area of current research: Keeping Track of Time, and Temporal Representation; Memory, Awareness and the Past; Memory and Experience; Knowledge and the Past: The Epistemology and Metaphysics of Time. A general introduction gives an overview of the topics discussed and makes explicit central themes which unify the different philosophical and psychological approaches.

2001, 440 p., Hardcover and paperback

ISBN-10: 0198250363
ISBN-13: 978-0198250364
You can read the book introduction here (PDF) Table of contents Search inside this book

Read more... Comments (1)

Are conscious and nonconscious processes supported by overlapping brain regions? In a recent study, Slotnick and Schacter investigated whether activity, related to visual memory, in early visual regions (BA17 and BA18) is reflective of nonconscious processing. The results of their study suggest that early visual regions (BA17, BA18) are associated with nonconcsious memory, while late visual regions (BA19, BA37) are associated with conscious memory. Click through for abstract. Hubmed.

Read more... Comments (0)

Brain stimulation provides an interesting tool to study the functions of a given area of the brain. In a study by Vignal et al. published in Brain, artificial stimulation or seizures in specific mesial temporal lobe structures were assessed both in terms of location and phenomenology.

Among the findings, the researchers found that “Forty-five per cent of dreamy states were evoked by stimulation of the amygdala, 37.5% by the hippocampus and 17.5% by the para-hippocampal gyrus.”

Furthermore, they found that their study “demonstrates the existence of large neural networks that produce recall of memories via activation of the hippocampus, amygdala and rhinal cortex.”

Read more... Comments (2)

Transcranial application of low-frequency electrical current during early nocturnal sleep potentiates the subject’s ability to remember words memorized the night before, German neuroendocrinologists report in this week’s online issue of Nature.

It is widely believed that sleep is linked with the long-term consolidation of new memories, via slow potential oscillations < 1 Hz that arise from the prefrontal neocortex, the research team at the University of Lubeck explains. However, many consider oscillations in brain potentials to be “mere epiphenomena.”

Read more... Comments (0)

The levels of a chemical released by the brain determine how detailed a memory will later be, according to researchers at UC Irvine.

The neurotransmitter acetylcholine, a brain chemical already established as being crucial for learning and memory, appears to be the key to adding details to a memory. In a study with rats, Norman Weinberger, research professor of neurobiology and behavior, and colleagues determined that a higher level of acetylcholine during a learning task correlated with more details of the experience being remembered. The results are the first to tie levels of acetylcholine to memory specificity and could have implications in the study and treatment of memory-related disorders.

Read more... Comments (0)

Hippocampus has a special issue on episodic memory and how it is studied. It is a comprehensive and thought provoking gathering of some of the front-end researchers in this field. Among the claims made in this issue, one can mention Ferbinteanu, Kennedy and Shapiro’s claim that

autonoetic experience is a feature of human consciousness rather than an obligatory aspect of memory for episodes, and that episodic memory is reconstructive and thus its key features can be modeled in animal behavioral tasks that do not involve either autonoetic consciousness or one-trial learning

Hoz and Wood argue that

mental time travel is the key feature of episodic memory and that it should take a form, in the awake animal, similar to the replay of behavioral patterns of activity that has been observed in hippocampus during sleep

Read more... Comments (0)