This is a preliminary review of new results on trace This is a - PowerPoint PPT Presentation

1 All- All -Russian Russian Conference Conference with with International International Participation Participation “HIPPOCAMPUS AND MEMORY: HIPPOCAMPUS AND MEMORY: NORM AND PATHOLOGY NORM AND PATHOLOGY” ” “ Pushchino, , Russia Russia Pushchino July 25- -28, 2009 28, 2009 July 25 THE ROLE OF THE HIPPOCAMPUS IN TRACE CONDITIONING. THE ROLE OF THE HIPPOCAMPUS IN TRACE CONDITIONING. Hegumen Theophan (V.I.Kryukov Hegumen Theophan ( V.I.Kryukov) ) St. Daniel Monastery, Moscow St. Daniel Monastery, Moscow This is a preliminary review of new results on trace This is a preliminary review of new results on trace conditioning that attempts to integrate them into conditioning that attempts to integrate them into the framework of Vinogradova Vinogradova’ ’s s (2001) Theta (2001) Theta- - the framework of Regulated Attention Theory. Regulated Attention Theory.

2 VINOGRADOVA’ ’S S CA3 COMPARATOR HYPOTHESIS: VINOGRADOVA CA3 COMPARATOR HYPOTHESIS: REPLY TO LISMAN LISMAN (2006) REPLY TO (2006) 1. Lisman Lisman (2006) states that (2006) states that “ “this hypothesis poses a difficulty; even this hypothesis poses a difficulty; even 1. Vinogradova Vinogradova claims that septal responses are usually claims that septal responses are usually polymodal polymodal. If this is . If this is correct then a CA3 comparator could not use septal information to decide correct then a CA3 comparator could not use septal information t o decide whether incoming information is novel or not” ” (p.37). (p.37). whether incoming information is novel or not 2. Lisman Lisman (1999) and (1999) and Lisman Lisman et al (2005) proposed an alternative hypothesis et al (2005) proposed an alternative hypothesis - - 2. that the comparator is in CA1, and not in CA3, because CA3 store that the comparator is in CA1, and not in CA3, because CA3 stores s temporal/permanent memories, and sends them to CA1 along with direct rect temporal/permanent memories, and sends them to CA1 along with di sensory information from entorhinal entorhinal cortex. cortex. sensory information from 3. Kryukov Kryukov (2008) argues that (2008) argues that Vinogradova Vinogradova’ ’s s theory requires the CA3 theory requires the CA3 3. comparator neither to be modality specific, nor to be storing an comparator neither to be modality specific, nor to be storing any memory traces, y memory traces, but it allows for solving the novelty detection problem uniformly, for all signal y, for all signal but it allows for solving the novelty detection problem uniforml modalities, because novelty detection is an emerging property of the whole PLL the whole PLL modalities, because novelty detection is an emerging property of system, and not just a single part of it. system, and not just a single part of it. 4. Vinogradova 4. Vinogradova’ ’s s theory backed by new data suggested new hypothesis to be theory backed by new data suggested new hypothesis to be proposed, that the hippocampus can function as a dual CA1- -CA3 comparator CA3 comparator proposed, that the hippocampus can function as a dual CA1 and thus resolving many difficult problems in classical conditioning. ning. and thus resolving many difficult problems in classical conditio

THETA- -REGULATED ATTENTION THEORY REGULATED ATTENTION THEORY - - BASIC THETA BASIC 3 FEATURES FEATURES (Vinogradova, 2001) 2001) (Vinogradova, • • The theta rhythm and the heta rhythm and the septo septo- -hippocampal system play a key role hippocampal system play a key role The t in the processes of selective perception, attention, and memory in the processes of selective perception, attention, and memory involving detection of novel and significant changes which should be involving detection of novel and significant changes which should be recorded in memory. memory. recorded in • • The CA1 field- -based information subsystem and the CA3 field based information subsystem and the CA3 field- -based based The CA1 field regulatory subsystem jointly perform the functions of attention and initial and initial regulatory subsystem jointly perform the functions of attention recording of new memory traces. recording of new memory traces. • • The CA3 field compares the two main inputs to the hippocampus – – The CA3 field compares the two main inputs to the hippocampus septal and cortical. Its output regulates the arousal and the theta heta- - septal and cortical. Its output regulates the arousal and the t rhythm frequency, and monitors the information CA3- -based subsystem. based subsystem. rhythm frequency, and monitors the information CA3 • • The CA1 field- -based subsystem is circular or spiral delay line with based subsystem is circular or spiral delay line with The CA1 field variable times of delay and simultaneously is the main hippocampal al variable times of delay and simultaneously is the main hippocamp . structures . output to the related cortical and subcortical subcortical structures output to the related cortical and

THEORY OF THETA- -REGULATED ATTENTION: RADAR REGULATED ATTENTION: RADAR THEORY OF THETA 4 ANALOGY ANALOGY (Vinogradova, 1975; Kryukov, 1991) (Vinogradova, 1975; Kryukov, 1991) The main function of the hippocampus is to compare the new and existing xisting The main function of the hippocampus is to compare the new and e traces. Via the feedback system, a mismatch signal will regulate the frequency the frequency traces. Via the feedback system, a mismatch signal will regulate of the theta rhythm, replaying the cortical traces and strengthening them on ning them on of the theta rhythm, replaying the cortical traces and strengthe repetition. repetition.

5 DOMINANT ARCHITECTURE OF "NEUROLOCATOR" DOMINANT ARCHITECTURE OF "NEUROLOCATOR" (Kryukov et al, 1990; 1990; Hegumen Theophan, Hegumen Theophan, 2004) 2004) (Kryukov et al, • • The functional unit is a cortical oscillator (CO) composed of integrate tegrate- - The functional unit is a cortical oscillator (CO) composed of in and- -fire neurons in a network fire neurons in a network with local excitation links, recurrent with local excitation links, recurrent and inhibition and non- -specific inputs from specific inputs from mRF mRF. . inhibition and non • • A septal septal oscillator (SO) serves as a coordinator oscillator (SO) serves as a coordinator A ("orchestra conductor "orchestra conductor“ “) for cortical ) for cortical oscillators during oscillators during ( information recording and replay. The two- -way link is way link is information recording and replay. The two non- -symmetrical, depending strongly on synchronization. symmetrical, depending strongly on synchronization. non • • Attention is switched from one CO group to Attention is switched from one CO group to another either by way of reset or through an automatic change of the another either by way of reset or through an automatic change of the SO frequency by a signal from the comparator output. SO frequency by a signal from the comparator output. • • Information is recorded in an ensemble of locally linked cortical l Information is recorded in an ensemble of locally linked cortica oscillators whose lability is modified upon training in accordance with the modified upon training in accordance with the oscillators whose lability is phenomenon of the dominant rhythm assimilation. phenomenon of the dominant rhythm assimilation.

6 KEY ASSUMPTIONS OF "NEUROLOCATOR" KEY ASSUMPTIONS OF "NEUROLOCATOR" (Kryukov et al, 1991) 1991) (Kryukov et al, • • The model structure is similar to that of a standard phase- -locked loop locked loop The model structure is similar to that of a standard phase (PLL), and at the same time, is arranged much like the regulatory (PLL), and at the same time, is arranged much like the regulator y subsystem of the limbic system, with the septum acting as the central ntral subsystem of the limbic system, with the septum acting as the ce pacemaker and the CA3 field being a comparator (Vinogradova Vinogradova 1975, 1975, pacemaker and the CA3 field being a comparator ( 2001 ). 2001 ). • • All COs serve as feature analyzers. They are inactive without specific pecific All COs serve as feature analyzers. They are inactive without s inputs and fairly high arousal is essential for initiation of oscillations in the scillations in the inputs and fairly high arousal is essential for initiation of o Θ / γ Θ / γ frequency range. frequency range. • • Attention is an emergent feature of the system, which appears with an ith an Attention is an emergent feature of the system, which appears w increase of arousal and manifests itself as transient synchronization of SO ation of SO increase of arousal and manifests itself as transient synchroniz with a certain group of COs. with a certain group of COs. • • Learning and consolidation rely on space space- -frequency plasticity frequency plasticity , involving , involving Learning and consolidation rely on gradual changes in the natural frequency of COs towards the sync gradual changes in the natural frequency of COs towards the sync frequency in the learning process. frequency in the learning process.