Abstract
Neural oscillations have been recorded and implicated in many different basic brain and cognitive processes. For example, oscillatory neural activity has been suggested to play a role in binding and in the maintenance of information in working memory. With respect to the latter, the majority of work has focused primarily on oscillations in terms of providing a “code” in working memory. However, oscillations may additionally play a fundamental role by enabling or facilitating essential properties and behaviors that neuronal networks must exhibit in order to produce functional working memory and the processes it supports, such as combining items in memory into bound objects or separating bound objects into distinct items. In the present work, we present a biologically plausible working memory model and demonstrate that specific types of stable oscillatory dynamics that arise may play critical roles in providing mechanisms for working memory and the cognitive functions that it supports. Specifically, these roles include (1) enabling a range of different types of binding, (2) both enabling and limiting capacities of bound and distinct items held active in working memory, and (3) facilitating transitions between active working memory states as required in cognitive function. Several key results arise within the examinations, such as the occurrence of different network capacities for working memory and binding, differences in processing times for transitions in working memory states, and the emergence of a combinatorially rich and complex range of oscillatory states that are sufficient to map onto a wide range of cognitive operations supported by working memory, such as variable binding, reasoning, and language. In particular, we show that these oscillatory states and their transitions can provide a specific instantiation of current established connectionist models in representing these functions. Finally, we further characterize the dependence of the relevant oscillatory solutions on certain critical parameters, including mutual inhibition and synaptic timescales.
Highlights
The neuronal substrate of working memory is thought to be persistent elevated firing rates of neurons that have been found in numerous physiological and imaging studies across widelyvarying scales, from single neurons up to neuronal populations and networks [1,2,3,4,5,6]
Working memory is a form of limited-capacity short term memory that is relevant to cognition
Since previous experimental and computational studies suggest NMDA receptors may be crucial to the persistent elevated firing rates associated with proper working memory function in experimental and computational studies, we model the effect of NMDA receptors as a separate component [2, 28,29,30,31]: u0j 1⁄4 À uj þ f ðaee u~j À aei ~vj þ aen n~j À ye þ sjðtÞÞ
Summary
The neuronal substrate of working memory is thought to be persistent elevated firing rates of neurons that have been found in numerous physiological and imaging studies across widelyvarying scales, from single neurons up to neuronal populations and networks [1,2,3,4,5,6]. Cognitive and behavioral considerations further imply that mechanisms must exist for rapidly transitioning between sequences of active memories, and that multiple (and possibly overlapping) selective populations and networks can be simultaneously active. These factors apply both to the case of neural binding, in which the activity of disparate neuronal populations or networks must be combined and maintained (e.g., corresponding to different aspects of a particular item in memory or working memory task), and for the case in which multiple different items are simultaneously maintained in working memory. One of the fundamental properties of working memory is that it has a limited capacity, possibly limited to three to five objects [7,8,9,10,11]
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