“Change the mind and you change the brain”: effects of cognitive-behavioral therapy on the neural correlates of spider phobia

Abstract

Questions pertaining to the neurobiological effects of psychotherapy are now considered among the most topical in psychiatry. With respect to this issue, positron emission tomography (PET) findings indicate that cognitive and behavioral modifications, occurring in a psychotherapeutic context, can lead to regional brain metabolic changes in patients with major depression or obsessive-compulsive disorder. The goal of the present functional magnetic resonance imaging (fMRI) study, which constitutes the first neuroimaging investigation of the effects of cognitive-behavioral therapy (CBT) using an emotional activation paradigm, was to probe the effects of CBT on the neural correlates of spider phobia. In order to do so, fMRI was used in subjects suffering from spider phobia (n = 12) to measure, before and after effective CBT, regional brain activity during the viewing of film excerpts depicting spiders. Normal control subjects were also scanned (once) while they were exposed to the same film excerpts. Results showed that, in phobic subjects before CBT, the transient state of fear triggered, during the viewing of the phobogenic stimuli, was correlated with significant activation of the right dorsolateral prefrontal cortex (Brodmann area—BA 10), the parahippocampal gyrus, and the visual associative cortical areas, bilaterally. For normal control subjects (n = 13), only the left middle occipital gyrus and the right inferior temporal gyrus were significantly activated. In phobic subjects before CBT, the activation of the dorsolateral prefrontal cortex (BA 10) may reflect the use of metacognitive strategies aimed at self-regulating the fear triggered by the spider film excerpts, whereas the parahippocampal activation might be related to an automatic reactivation of the contextual fear memory that led to the development of avoidance behavior and the maintenance of spider phobia. After successful completion of CBT, no significant activation was found in the dorsolateral prefrontal cortex (BA 10) or the parahippocampal gyrus. These findings suggest that a psychotherapeutic approach, such as CBT, has the potential to modify the dysfunctional neural circuitry associated with anxiety disorders. They further indicate that the changes made at the mind level, within a psychotherapeutic context, are able to functionally “rewire” the brain.

Introduction

Specific phobias are the most common psychiatric disorders, with an estimated lifetime prevalence of 11.3% in the United States (Magee et al., 1996). Spider phobia (SP) is one of the most widespread forms of specific phobia (Bourdon et al., 1988). People with SP experience persistent and intense fear when confronted with spiders and develop avoidance behavior of all contexts related to this animal (APA, 1994).

To date, a few functional brain imaging studies have been carried out to map the neural substrate of SP. In the first two of this series of studies, subjects were scanned with positron emission tomography (PET) while they were viewing a color videotape of a spider Flavell 1979, Fredrikson et al 1993, Fredrikson et al 1995. Fear and anxiety associated with phobic stimulation increased regional cerebral blood flow (rCBF) in the visual associative cortex and decreased rCBF in the hippocampus, posterior cingulate, orbitofrontal, prefrontal, and temporopolar cortices. These findings were construed to mean that the rCBF increase in the visual associative cortex might reflect increased visual attention to the significance (potential threat) of the stimulus whereas the reduced rCBF activity in limbic and paralimbic cortices might reflect reduced conscious cognitive processing during the cerebral response associated with the defense reaction. In another of these PET studies (Rauch et al., 1995), subjects suffering from specific phobias were asked to close their eyes and to allow their thoughts to focus on their individualized phobogenic stimulus (e.g., a container with the feared animal inside— spider, snake, bees, rat) which was placed near the subjects. Significant rCBF increases were found in the anterior cingulate, insular, anterior temporal, and medial orbitofrontal cortices. Activation of these limbic/paralimbic regions was interpreted as being associated with autonomic hyperactivity and exaggerated anxiety response to the phobogenic stimulus. More recently, subjects suffering from SP were scanned—using the ¹³³Xe inhalation method—while they were exposed to a video showing living spiders Husain and Kennard 1996, Johanson et al 1998. Half of the subjects showed severe panic during the spider exposure and had marked rCBF decreases in right frontal cortex. The remaining subjects became frightened, but not panic stricken, during spider exposure and showed a rCBF increase in the right frontal cortical area. This frontal rCBF increase was hypothesized to be correlated with the use of cognitive strategies for coping with the phobic situation.

Questions pertaining to the neurobiological effects of psychotherapy are now considered among the most topical in psychiatry Kandel 1999, Gabbard 2000, Thase 2001. With respect to this issue, recent PET findings indicate that psychotherapy can lead to regional brain metabolic changes in patients with major depression Bourdon et al 1988, Martin et al 2001. Along the same lines, a few PET studies have demonstrated that successful cognitive-behavioral therapy (CBT) of obsessive-compulsive disorder is associated with significant changes in glucose metabolic rates within various brain regions Bandura 1997, Schwartz et al 1996. In all these PET studies, metabolic changes were measured during resting state.

CBT is an effective psychotherapeutic approach for reducing the symptoms of specific phobias Öst 1989, Öst 1996, American Psychiatric Association (APA) 1994. This form of therapy consists of exposure-based treatment to the phobogenic stimuli (e.g., spiders) combined with education for changing negative cognitive misattributions related to these stimuli. Although several psychological models have been proposed to explain the therapeutic effects of CBT, little is known regarding the neurobiological mechanisms underlying this form of psychotherapy.

The main goal of the present functional magnetic resonance imaging (fMRI) study, which constitutes the first neuroimaging investigation of the effects of CBT using an emotional activation paradigm, was to probe the effects of CBT on the neural correlates of SP. A more general objective of this study was to investigate how changes made at the mind level, within a psychotherapeutic context, are transduced at the neurobiological level. Subjects suffering from this specific form of phobia were scanned, before and after CBT, while they were viewing film excerpts showing either living spiders (activation task) or living butterflies (reference task). We predicted a priori that successful completion of CBT would be accompanied by a marked reduction of activity in the brain regions (prefrontal cortex, hippocampal/parahippocampal region, visual associative cortex) associated with SP.