Remembrance of things future: Long-term memory sets the stage for visual perception
Experimental protocol for memory-guided attention. (A) In both EEG and fMRI experiments, participants first completed a learning task in which they searched for a target stimulus that was embedded within naturalistic scenes. Targets were presented on the right (Right Memory), left (Left Memory) or not at all (Neutral Memory). (B) Over repeated sessions, participants found, and learned, the location of target stimuli. The learning profile from the EEG experiment is plotted for search accuracy (left y axis, red) and search time (right y axis, blue) as a function of training session number (x axis). (C) On the following day, participants performed an attention task in which scenes from the initial learning task were used to cue the location of a subsequent target. The first scene was always presented without the target stimulus, whereas the second scene contained a target on 50% of trials. On target-present trials, previously learned locations were 100% predictive of the subsequent target location. Consequently, valid memory cue scenes could be used to predict the precise location of the subsequent target, whereas memories for neutral cues contained no task-relevant spatial information. (D) Behavioral data are shown for the EEG experiment, with sensitivity (left y axis, bars) and RT (right y axis, triangles) plotted as a function memory condition (memory vs. neutral). Detection sensitivity was higher for spatially predictive memories, and RTs were shorter. Error bars represent ±1 SEM. Copyright © PNAS, doi: 10.1073/pnas.1108555108
(Medical Xpress) -- Rather than being a passive state, perception is an active process fueled by predictions and expectations about our environment. In the latter case, memory must be a fundamental component in the way our brain generates these precursors to the perceptual experience – but how the brain integrates long-term memory with perception has not been determined. Recently, however, researchers in the Department of Experimental Psychology at the University of Oxford, by devising a method for integrating memory and attention, showed how LTM optimizes perception by varying brain states associated with anticipation of spatial localization in the visual field. The scientists also used fMRI to articulate a neural network involving a number of cortical areas likely to be active in the predictive use of memory in the visual cortex.
Lead researcher Mark G. Stokes, working with Kathryn Atherton, Eva Zita Patai, and Anna Christina Nobre, explains that to study how memory guides attention, it was first necessary to train each participant of the experiment to remember a large number of associations that can then be used to guide attention. “In this study,” Stokes tells Medical Xpress, “we exploited the brain’s inherent ability to remember specific spatial locations within natural scenes. Despite the enormous visual complexity in such scenes, the brain is extremely adept at processing this kind of information, and can store essential details in long-term memory with little apparent effort. This ability is an ideal route for us to experimentally manipulate the contents of long-term memory to test the effects of attention on visual performance, and explore the underlying brain basis with EEG and fMRI.”
Memory predictions trigger contralateral alpha-desynchronization in posterior electrodes. (A) EEG recordings demonstrate that memory cues trigger spatially specific desynchronization of alpha-band oscillations in posterior electrodes, including PO7/PO8. The scalp topography of cue-specific differences (left − right cue; 650-750 ms) in alpha power is shown projected across a 3D scalp surface. (B) Time-course analysis of alpha power in lateralized posterior electrodes, PO7 (in red) and PO8 (in blue), illustrates how contralateral desynchronization emerges at approximately 400 ms after the cue onset. Positive values reflect contralateral desynchronization in the left hemisphere, whereas negative values reflect desynchronization in the right hemisphere, and shading represents ±1 SEM. Copyright © PNAS, doi:10.1073/pnas.1108555108To accomplish this, says Stokes, the key methodological development in their research was to specifically measure how long-term memories modulate preparatory brain activity. “For the fMRI experiment, this involved a technique called event-related fMRI, which allows us to separate statistically the brain response to distinct cognitive events. Incorporating high-temporal resolution EEG was also a key innovation in this research, providing a more direct real-time measure of memory related changes in preparatory brain activity.”
The next step in the team’s research was to determine how an integrated circuit of attention and memory related brain areas – the frontoparietal cortex, and hippocampus, respectively – are coordinated for memory-guided attention. “So far we’ve demonstrated which brain areas are active,” Stokes notes, “but more detailed imaging data could also tell us how these areas communicate. Moreover, disruption methods like Transcranial Magnetic Stimulation can pinpoint which nodes of the frontoparietal network are necessary for memory guided attention.”
Memory predictions increase BOLD-related activity in contralateral visual areas. (A) Behavioral analysis of fMRI experiment confirmed that detection sensitivity was enhanced for targets presented at memory-predicted locations, relative to memory-neutral locations. Detection sensitivity (left y axis, bars) and RT (right y axis, triangles) are plotted as a function memory condition (memory valid vs. neutral). (B) Analysis of the BOLD response revealed evidence of spatially specific biases in preparatory visual activity: memory cues elicited increased activity in contralateral subregions of visual cortex, particularly in extrastriate visual areas. Data contrasting left vs. right views are shown on the occipital surface, extracted and flattened using Freesurfer (Materials and Methods) (C) Spatially specific cue-related activity is shown for specific visual areas (text provides details). Error bars represent ±1 SEM. Copyright © PNAS, doi:10.1073/pnas.1108555108Commenting on how their findings might impact other areas, Stokes points out that integrating high-spatial resolution fMRI and high-temporal resolution EEG would be a powerful approach for a range of cognitive neuroscience applications. It also might be possible, Stokes agrees, to transition to a completely in silico model based on optogenetics-derived data.
More information: Long-term memory prepares neural activity for perception, PNAS, Published online before print November 22, 2011, doi: 10.1073/pnas.1108555108
Copyright 2011 Medical Xpress.
All rights reserved. This material may not be published, broadcast, rewritten or redistributed in whole or part without the express written permission of PhysOrg.com.
- Human working memory is based on dynamic interaction networks in the brain Apr 13, 2010 | not rated yet | 0
- Sea snails help researchers explore a way to enhance memory Dec 26, 2011 | not rated yet | 0
- Study indicates how we maintain visual details in short-term memory Feb 20, 2009 | not rated yet | 0
- Echoes discovered in early visual brain areas play role in working memory Feb 18, 2009 | not rated yet | 0
- Regulation of attention and concentration in brain unravelled Aug 11, 2011 | not rated yet | 0
- Motion perception revisited: High Phi effect challenges established motion perception assumptions Apr 23, 2013 | 3 / 5 (2) | 2
- Anything you can do I can do better: Neuromolecular foundations of the superiority illusion (Update) Apr 02, 2013 | 4.5 / 5 (11) | 5
- The visual system as economist: Neural resource allocation in visual adaptation Mar 30, 2013 | 5 / 5 (2) | 9
- Separate lives: Neuronal and organismal lifespans decoupled Mar 27, 2013 | 4.9 / 5 (8) | 0
- Sizing things up: The evolutionary neurobiology of scale invariance Feb 28, 2013 | 4.8 / 5 (10) | 14
Why is zone 1 in liver more prone to ischemic injury?
May 23, 2013 Hi, Is it because around central vein, there is only deoxygenated blood from the vein where as in the periphery there is hepatic artery. Also why...
How can there be villous adenoma in colon, if there are no villi there
May 22, 2013 As title suggest. Thanks :smile:
How can there be a term called "intestinal metaplasia" of stomach
May 21, 2013 Hello everyone, Ok Stomach's normal epithelium is simple columnar, now in intestinal type of adenocarcinoma of stomach it undergoes "intestinal...
Pressure-volume curve: Elastic Recoil Pressure don't make sense
May 18, 2013 From pressure-volume curve of the lung and chest wall (attached photo), I don't understand why would the elastic recoil pressure of the lung is...
If you became brain-dead, would you want them to pull the plug?
May 17, 2013 I'd want the rest of me to stay alive. Sure it's a lousy way to live but it beats being all-the-way dead. Maybe if I make it 20 years they'll...
MRI bill question
May 15, 2013 Dear PFers, The hospital gave us a $12k bill for one MRI (head with contrast). The people I talked to at the hospital tell me that they do not...
- More from Physics Forums - Medical Sciences
More news stories
New research presented today shows that formation of new neurons in the hippocampus - a brain region known for its importance in learning and remembering - could cause forgetting of old memories by causing a reorganization ...
Neuroscience 14 hours ago | 4 / 5 (4) | 0
How can healthy people who hear voices help schizophrenics? Finding the answer for this is at the centre of research conducted at the University of Bergen.
Neuroscience 14 hours ago | 4 / 5 (2) | 2
One of the major frontiers of modern science is a comprehensive understanding of the human brain and its functions to guide the development of new technologies in information and communication. In a major announcement for ...
Neuroscience 15 hours ago | 3.7 / 5 (3) | 0
(Medical Xpress)—Regulating the distribution of power in neurons is done by a system that makes the national electric grid look simple by comparison. Each neuron has several thousand mitochondria confined ...
Neuroscience May 23, 2013 | 4.9 / 5 (9) | 0 |
(Medical Xpress)—The human brain is able to identify individuals' voices by comparing them against an internal 'average voice' prototype, according to neuroscientists.
Neuroscience May 23, 2013 | 3 / 5 (2) | 3 |
(Medical Xpress)—A new study by researchers in the US has shown that an ancient virus can be modified to help in the fight against the simian immunodeficiency virus SIV, which is the equivalent in monkeys ...
15 hours ago | 5 / 5 (3) | 0 |
Two mutations central to the development of infantile myofibromatosis (IM)—a disorder characterized by multiple tumors involving the skin, bone, and soft tissue—may provide new therapeutic targets, according to researchers ...
9 hours ago | 3 / 5 (2) | 0 |
Women at a particular stage in their monthly menstrual cycle may be more vulnerable to some of the psychological side-effects associated with stressful experiences, according to a study from UCL.
11 hours ago | 3.7 / 5 (3) | 0 |
Biological processes are generally based on events at the molecular and cellular level. To understand what happens in the course of infections, diseases or normal bodily functions, scientists would need to ...
12 hours ago | 5 / 5 (4) | 0 |
Talking on a hands-free device while behind the wheel can lead to a sharp increase in errors that could imperil other drivers on the road, according to new research from the University of Alberta.
8 hours ago | not rated yet | 0
(Medical Xpress)—Patients with diabetes who are depressed are much more likely to develop episodes of dangerously low blood sugars, or hypoglycemia, than are those who are not depressed, a new study has ...
16 hours ago | not rated yet | 0 |