First Steps in Using Multi-Voxel Pattern Analysis to Disentangle Neural Processes Underlying Generalization of Spider Fear.

Renée M Visser,Merel Kindt,Robert J Zwitser,Pia Haver,H Steven Scholte

doi:10.3389/fnhum.2016.00222

Renée M Visser, Merel Kindt + Show 3 more

Open Access

https://doi.org/10.3389/fnhum.2016.00222

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Abstract

A core symptom of anxiety disorders is the tendency to interpret ambiguous information as threatening. Using electroencephalography and blood oxygenation level dependent magnetic resonance imaging (BOLD-MRI), several studies have begun to elucidate brain processes involved in fear-related perceptual biases, but thus far mainly found evidence for general hypervigilance in high fearful individuals. Recently, multi-voxel pattern analysis (MVPA) has become popular for decoding cognitive states from distributed patterns of neural activation. Here, we used this technique to assess whether biased fear generalization, characteristic of clinical fear, is already present during the initial perception and categorization of a stimulus, or emerges during the subsequent interpretation of a stimulus. Individuals with low spider fear (n = 20) and high spider fear (n = 18) underwent functional MRI scanning while viewing series of schematic flowers morphing to spiders. In line with previous studies, individuals with high fear of spiders were behaviorally more likely to classify ambiguous morphs as spiders than individuals with low fear of spiders. Univariate analyses of BOLD-MRI data revealed stronger activation toward spider pictures in high fearful individuals compared to low fearful individuals in numerous areas. Yet, neither average activation, nor support vector machine classification (i.e., a form of MVPA) matched the behavioral results – i.e., a biased response toward ambiguous stimuli – in any of the regions of interest. This may point to limitations of the current design, and to challenges associated with classifying emotional and neutral stimuli in groups that differ in their judgment of emotionality. Improvements for future research are suggested.

Highlights

The ability to recognize threatening stimuli clearly increases the chances of survival
We examined in a datadriven manner whether overgeneralization of fear is associated with functional anomalies in regions traditionally associated with (1) early perception and object identification (Ungerleider and Haxby, 1994), which would support a perceptual account, and/or 2) regions involved in saliency (Etkin and Wager, 2007; Seeley et al, 2007; Hermans et al, 2011; Ipser et al, 2013), and higher cognitive processes (Miller and Cohen, 2001), which would support a more conceptual account
In the high spider fear (HSF) group classification was above chance in amygdala, insula, anterior cingulate cortex, supramarginal gyrus, and the precentral gyrus

Summary

Introduction

The ability to recognize threatening stimuli clearly increases the chances of survival. Stimulus generalization —a learning mechanism whereby conditioned responses extend to a range of stimuli. Spider Fear and Multi-Voxel Pattern Analysis resembling the original conditioned stimuli (Pavlov, 1927) – enables a fast response to novel potentially threatening stimuli. It can turn into maladaptive behavior when non-threatening stimuli or contexts are inappropriately treated as harmful. We will refer to this phenomenon as ‘overgeneralization of fear’ or ‘maladaptive fear generalization.’. The way we use the term ‘fear’ here includes both physiological and behavioral responses to threat, as well as the subjective experience of fear (but see for an alternative use of the term ‘fear’ LeDoux, 2014) We will refer to this phenomenon as ‘overgeneralization of fear’ or ‘maladaptive fear generalization.’ The way we use the term ‘fear’ here includes both physiological and behavioral responses to threat, as well as the subjective experience of fear (but see for an alternative use of the term ‘fear’ LeDoux, 2014)

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