The Relationship between Working Memory Storage and Elevated Activity as Measured with Functional Magnetic Resonance Imaging

Departments of Psychology and Psychiatry, University of Wisconsin-Madison, Madison, Wisconsin 53706.
The Journal of Neuroscience : The Official Journal of the Society for Neuroscience (Impact Factor: 6.34). 09/2012; 32(38):12990-8. DOI: 10.1523/JNEUROSCI.1892-12.2012
Source: PubMed


Does the sustained, elevated neural activity observed during working memory tasks reflect the short-term retention of information? Functional magnetic resonance imaging (fMRI) data of delayed recognition of visual motion in human participants were analyzed with two methods: a general linear model (GLM) and multivoxel pattern analysis. Although the GLM identified sustained, elevated delay-period activity in superior and lateral frontal cortex and in intraparietal sulcus, pattern classifiers were unable to recover trial-specific stimulus information from these delay-active regions. The converse-no sustained, elevated delay-period activity but successful classification of trial-specific stimulus information-was true of posterior visual regions, including area MT+ (which contains both middle temporal area and medial superior temporal area) and calcarine and pericalcarine cortex. In contrast to stimulus information, pattern classifiers were able to extract trial-specific task instruction-related information from frontal and parietal areas showing elevated delay-period activity. Thus, the elevated delay-period activity that is measured with fMRI may reflect processes other than the storage, per se, of trial-specific stimulus information. It may be that the short-term storage of stimulus information is represented in patterns of (statistically) "subthreshold" activity distributed across regions of low-level sensory cortex that univariate methods cannot detect.

Download full-text


Available from: Bradley R Postle, Aug 05, 2014
  • Source
    • "The neural signature of the FOA appears to be fronto - parietal modulation of the neural representations in sensory regions engaged in memory maintenance ( Feredoes et al . , 2011 ; Riggall and Postle , 2012 ; Emrich et al . , 2013 ) . "
    [Show abstract] [Hide abstract]
    ABSTRACT: What is the role of top-down attentional modulation in consciously accessing working memory (WM) content? In influential WM models, information can exist in different states, determined by allocation of attention; placing the original memory representation in the center of focused attention gives rise to conscious access. Here we discuss various lines of evidence indicating that such attentional modulation is not sufficient for memory content to be phenomenally experienced. We propose that, in addition to attentional modulation of the memory representation, another type of top-down modulation is required: suppression of all incoming visual information, via inhibition of early visual cortex. In this view, there are three distinct memory levels, as a function of the top-down control associated with them: (1) Nonattended, nonconscious associated with no attentional modulation; (2) attended, phenomenally nonconscious memory, associated with attentional enhancement of the actual memory trace; (3) attended, phenomenally conscious memory content, associated with enhancement of the memory trace and top-down suppression of all incoming visual input.
    Frontiers in Psychology 11/2015; 6:1603. DOI:10.3389/fpsyg.2015.01603 · 2.80 Impact Factor
  • Source
    • "What is commonly regarded as subthreshold activity has in recent times received an increased amount of attention. Assuring results from multivariate approaches (e.g., multi-voxel pattern analysis or MVPA) have found that activity that remains subthreshold in conventional univariate (general linear model) approaches is often meaningful by succeeding to recover stimulus-specific information (Riggall & Postle, 2013; Harrison & Tong, 2009; Serences et al., 2009; Sreenivasan et al., 2014; Reuter-Lorenz & Sylvester, 2005). According to this, the reliable area observed for Key Clarity (Fig. 3) may encode relevant information in scattered foci across brain areas that would have remained subthreshold in univariate analysis. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Low-level (timbral) and high-level (tonal and rhythmical) musical features during continuous listening to music, studied by functional magnetic resonance imaging (fMRI), have been shown to elicit large-scale responses in cognitive, motor and limbic brain networks. Using a similar methodological approach and a similar group of participants, we aimed to study replicability of previous findings. Participants' fMRI responses during continuous listening of a tango Nuevo piece were correlated voxelwise against time series of a set of perceptually validated musical features computationally extracted from the music. The replicability of previous results and the present study was assessed by two approaches: (a) correlating the respective activation maps; and (b) computing the overlap of active voxels between datasets at variable levels of ranked significance. Activity elicited by timbral features was better replicable than activity elicited by tonal and rhythmical ones. These results indicate more reliable processing mechanisms for low-level musical features as compared to more high-level features. The processing of such high-level features is probably more sensitive to state and traits of the listeners, as well as of their background in music.
    NeuroImage 09/2015; 124(Pt A). DOI:10.1016/j.neuroimage.2015.09.005 · 6.36 Impact Factor
  • Source
    • ", Zarahn et al . , 1997 ; Riggall and Postle , 2012 ) , we identified regions with elevated delay period activation with a random - effects general linear model ( GLM ) that included separate regressors marking the sample , delay , and probe epochs ( see Experimental Procedures ) . A statistical parametric map ( SPM ) showing cortical areas with elevated delay period activity is shown in Fig - ure 3 . "
    [Show abstract] [Hide abstract]
    ABSTRACT: Working memory (WM) enables the storage and manipulation of information in an active state. WM storage has long been associated with sustained increases in activation across a network of frontal and parietal cortical regions. However, recent evidence suggests that these regions primarily encode information related to general task goals rather than feature-selective representations of specific memoranda. These goal-related representations are thought to provide top-down feedback that coordinates the representation of fine-grained details in early sensory areas. Here, we test this model using fMRI-based reconstructions of remembered visual details from region-level activation patterns. We could reconstruct high-fidelity representations of a remembered orientation based on activation patterns in occipital visual cortex and in several sub-regions of frontal and parietal cortex, independent of sustained increases in mean activation. These results challenge models of WM that postulate disjoint frontoparietal "top-down control" and posterior sensory "feature storage" networks. Copyright © 2015 Elsevier Inc. All rights reserved.
    Neuron 08/2015; 87(4). DOI:10.1016/j.neuron.2015.07.013 · 15.05 Impact Factor
Show more