scholarly journals Towards understanding of the cortical network underlying associative memory

2008 ◽  
Vol 363 (1500) ◽  
pp. 2187-2199 ◽  
Author(s):  
Takahiro Osada ◽  
Yusuke Adachi ◽  
Hiroko M Kimura ◽  
Yasushi Miyashita
Keyword(s):  
Prefrontal Cortex ◽  
Medial Temporal Lobe ◽  
Temporal Cortex ◽  
Neural Mechanism ◽  
Neural Representation ◽  
Association Cortex ◽  
Retrieval Process ◽  
Top Down ◽  
Automatic Retrieval ◽  
Local Circuits

Declarative knowledge and experiences are represented in the association cortex and are recalled by reactivation of the neural representation. Electrophysiological experiments have revealed that associations between semantically linked visual objects are formed in neural representations in the temporal and limbic cortices. Memory traces are created by the reorganization of neural circuits. These regions are reactivated during retrieval and contribute to the contents of a memory. Two different types of retrieval signals are suggested as follows: automatic and active. One flows backward from the medial temporal lobe during the automatic retrieval process, whereas the other is conveyed as a top-down signal from the prefrontal cortex to the temporal cortex during the active retrieval process. By sending the top-down signal, the prefrontal cortex manipulates and organizes to-be-remembered information, devises strategies for retrieval and monitors the outcome. To further understand the neural mechanism of memory, the following two complementary views are needed: how the multiple cortical areas in the brain-wide network interact to orchestrate cognitive functions and how the properties of single neurons and their synaptic connections with neighbouring neurons combine to form local circuits and to exhibit the function of each cortical area. We will discuss some new methodological innovations that tackle these challenges.

Top-Down Signal of Retrieved Information From Prefrontal to Inferior Temporal Cortices

2007 ◽  
Vol 98 (4) ◽  
pp. 1965-1974 ◽  
Author(s):  
Masato Inoue ◽  
Akichika Mikami
Keyword(s):  
Working Memory ◽  
Prefrontal Cortex ◽  
Temporal Cortex ◽  
Inferior Temporal Cortex ◽  
Critical Area ◽  
Retrieval Process ◽  
Multiple Objects ◽  
Top Down ◽  
Ventrolateral Prefrontal Cortex

We compared neuronal activities in the ventrolateral prefrontal cortex (VLPFC) and the inferior temporal cortex (IT) during the retrieval of an object from the working memory. About one third of IT neurons showed color- and target-selective (CT) or target-selective (T) response during the color cue period of the serial probe reproduction (SPR) task. These object-selective (CT and T) responses in IT could be correlated with the retrieval process of an object from the memorized multiple objects because no objects were presented during this period. However, proportion of CT and T responses was smaller in IT than in VLPFC, where two thirds of neurons showed object-selective response. In addition, object-selective response started earlier in VLPFC than in IT. These results suggest that VLPFC retrieves particular object information from the working memory and sends the retrieved object information to IT. The fact that the responses in the error trials did not decrease in IT suggests that IT is not a critical area for the retrieval process from the working memory.

scholarly journals Tomita H, Ohbayashi M, Nakahara K, Hasegawa I, Miyashita Y

1999 ◽  
Vol 7 (6) ◽  
pp. E14
Author(s):  
William T. Couldwell
Keyword(s):  
Prefrontal Cortex ◽  
Executive Control ◽  
Temporal Cortex ◽  
Inferior Temporal Cortex ◽  
Association Cortex ◽  
Long Term Memory ◽  
Top Down ◽  
Visual Inputs ◽  
Voluntary Recall ◽  
Show Evidence

Knowledge or experience is voluntarily recalled from memory by reactivation of the neural representations in the cerebral association cortex. In inferior temporal cortex, which serves as the storehouse of visual long-term memory, activation of mnemonic engrams through electric stimulation results in imagery recall in humans, and neurons can be dynamically activated by the necessity for memory recall in monkeys. Neuropsychological studies and previous split-brain experiments predicted that prefrontal cortex exerts executive control upon inferior temporal cortex in memory retrieval; however, no neuronal correlate of this process has ever been detected. Here we show evidence of the top-down signal from prefrontal cortex. In the absence of bottom-up visual inputs, single inferior temporal neurons were activated by the top-down signal, which conveyed information on semantic categorization imposed by visual stimulus-stimulus association. Behavioural performance was severely impaired with loss of the top-down signal. Control experiments confirmed that the signal was transmitted not through a subcortical but through a fronto-temporal cortical pathway. Thus, feedback projections from prefrontal cortex to the posterior association cortex appear to serve the executive control of voluntary recall.

rCBF-activatie en neuronale circuits gerelateerd aan visuele waarneming

1996 ◽  
Vol 8 (2) ◽  
pp. 35-39
Author(s):  
B.M. de Jong
Keyword(s):  
Information Processing ◽  
Temporal Cortex ◽  
Distributed Networks ◽  
Association Cortex ◽  
Top Down ◽  
Primary Sensory Cortex ◽  
Visual Areas ◽  
Simultaneous Activation ◽  
Remote Association

SummaryThree principles of neuronal interaction within cortically distributed networks are discussed. PET-rCBF activation methods provide an opportunity to acquire insight in the distribution of functionally related areas of the human brain in vivo. The distinction of visual areas, activated by either motion or color within an observed scenery, points at a segregation in neuronal information processing. Such a segregation extends into both a dorsal and a ventral route towards consequently the parietal and temporal cortex.Simultaneous activation over the dorsal and ventral route, which for example occurs in relation to the perception of complex motion (optic flow), or motion perception after lesion of V5, suggests integration by means of cross-connectivity. The third principle, i.e. “top-down” integration, appears by analysis of V5-V1 interaction, attentional effects on V4, frontal activation in prosopagnosia, and by analysis of hallucinations. Such “top-down” integration indicates the presence of momentaneous effect on cortical areas, intimately related to the primary sensory cortex, by neuronal activity of remote “association” cortex, the latter being connected by direct (synaps-restricted) bypass from early stations of information processing.

scholarly journals Enhanced Bottom-Up and Reduced Top-Down fMRI Activity Is Related to Long-Lasting Nonreinforced Behavioral Change

2019 ◽  
Vol 30 (3) ◽  
pp. 858-874 ◽  
Author(s):  
Rotem Botvinik-Nezer ◽  
Tom Salomon ◽  
Tom Schonberg
Keyword(s):  
Behavioral Change ◽  
Neural Mechanism ◽  
Self Control ◽  
Neural Representation ◽  
Top Down ◽  
Bottom Up ◽  
Targeted Interventions ◽  
Approach Training ◽  
Term Change

Abstract Behavioral change studies and interventions focus on self-control and external reinforcements to influence preferences. Cue-approach training (CAT) has been shown to induce preference changes lasting months by merely associating items with neutral cues and speeded responses. We utilized this paradigm to study neural representation of preferences and their modification without external reinforcements. We scanned 36 participants with fMRI during a novel passive viewing task before, after and 30 days following CAT. We preregistered the predictions that activity in memory, top-down attention, and value-processing regions will underlie preference modification. While most theories associate preferences with prefrontal regions, we found that “bottom-up” perceptual mechanisms were associated with immediate change, whereas reduced “top-down” parietal activity was related to long-term change. Activity in value-related prefrontal regions was enhanced immediately after CAT for trained items and 1 month after for all items. Our findings suggest a novel neural mechanism of preference representation and modification. We suggest that nonreinforced change of preferences occurs initially in perceptual representation of items, putatively leading to long-term changes in “top-down” processes. These findings offer implementation of bottom-up instead of top-down targeted interventions for long-lasting behavioral change.

scholarly journals Reward learning over weeks versus minutes increases the neural representation of value in the human brain

2017 ◽  
Author(s):  
G. Elliott Wimmer ◽  
Jamie K. Li ◽  
Krzysztof J. Gorgolewski ◽  
Russell A. Poldrack
Keyword(s):  
Prefrontal Cortex ◽  
Temporal Lobe ◽  
Medial Temporal Lobe ◽  
Short Term Memory ◽  
Neural Representation ◽  
Reward Learning ◽  
Short Term ◽  
Term Memory ◽  
Feedback Learning ◽  
Over Time

AbstractOver the past few decades, neuroscience research has illuminated the neural mechanisms supporting learning from reward feedback. Learning paradigms are increasingly being extended to study mood and psychiatric disorders as well as addiction. However, one potentially critical characteristic that this research ignores is the effect of time on learning: human feedback learning paradigms are usually conducted in a single rapidly paced session, while learning experiences in ecologically relevant circumstances and in animal research are almost always separated by longer periods of time. In our experiments, we examined reward learning in short condensed sessions distributed across weeks vs. learning completed in a single “massed” session in male and female participants. As expected, we found that after equal amounts of training, accuracy was matched between the spaced and massed conditions. However, in a 3-week follow-up, we found that participants exhibited significantly greater memory for the value of spaced-trained stimuli. Supporting a role for short-term memory in massed learning, we found a significant positive correlation between initial learning and working memory capacity. Neurally, we found that patterns of activity in the medial temporal lobe and prefrontal cortex showed stronger discrimination of spaced-vs. massed-trained reward values. Further, patterns in the striatum discriminated between spaced-and massed-trained stimuli overall. Our results indicate that single-session learning tasks engage partially distinct learning mechanisms from spaced sessions of training. Our studies begin to address a large gap in our knowledge of human learning from reinforcement, with potential implications for our understanding of mood disorders and addiction.Significance statementHumans and animals learn to associate predictive value with stimuli and actions, and these values then guide future behavior. Such reinforcement-based learning often happens over long time periods, in contrast to most studies of reward-based learning in humans. In experiments that tested the effect of spacing on learning, we found that associations learned in a single massed session were correlated with short-term memory and significantly decayed over time, while associations learned in short massed sessions over weeks were well-maintained. Additionally, patterns of activity in the medial temporal lobe and prefrontal cortex discriminated the values of stimuli learned over weeks but not minutes. These results highlight the importance of studying learning over time, with potential applications to drug addiction and psychiatry.

scholarly journals Now You See One Letter, Now You See Meaningless Symbols: Perceptual and Semantic Hypnotic Suggestions Reduce Stroop Errors Through Different Neurocognitive Mechanisms

2021 ◽  
Vol 14 ◽  
Author(s):  
Rinaldo Livio Perri ◽  
Valentina Bianco ◽  
Enrico Facco ◽  
Francesco Di Russo
Keyword(s):  
Prefrontal Cortex ◽  
Executive Control ◽  
Temporal Cortex ◽  
Semantic Activation ◽  
Top Down ◽  
Sensory Awareness ◽  
Subject Design ◽  
Medium Level ◽  
Accurate Performance ◽  
Hypnotic Suggestions

Compelling literature has suggested the possibility of adopting hypnotic suggestions to override the Stroop interference effect. However, most of these studies mainly reported behavioral data and were conducted on highly hypnotizable individuals. Thus, the question of the neural locus of the effects and their generalizability remains open. In the present study, we used the Stroop task in a within-subject design to test the neurocognitive effects of two hypnotic suggestions: the perceptual request to focus only on the central letter of the words and the semantic request to observe meaningless symbols. Behavioral results indicated that the two types of suggestions did not alter response time (RT), but both favored more accurate performance compared to the control condition. Both types of suggestions increased sensory awareness and reduced discriminative visual attention, but the perceptual request selectively engaged more executive control of the prefrontal cortex (PFC), and the semantic request selectively suppressed the temporal cortex activity devoted to graphemic analysis of the words. The present findings demonstrated that the perceptual and the semantic hypnotic suggestions reduced Stroop errors through common and specific top-down modulations of different neurocognitive processes but left the semantic activation unaltered. Finally, as we also recruited participants with a medium level of hypnotizability, the present data might be considered potentially representative of the majority of the population.

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