Neurobiologial Etiology

Research Summaries

The Biological Psychology of Dissociative Identity Disorder Neurobiologial Etiology of DID

	THE FOLLOWING IS A SUMMARY OF SOME KEY CONCEPTS FROM: *Forrest, Kelly A. (2001). Toward an etiology of dissociative identity disorder: a neurodevelopmental approach. Consciousness and Cognition, 10, 259-293.*

Etiology of DID

Putnam's model of discrete behavioral states

Putnam proposed a developmental model of dissociative identity disorder. Behavioral states are defined as inclusive of all mental and emotional functioning. Putnam theorizes that children create behavioral states in differing environments and interpersonal interactions, and the process of maturation is "consolidating an integrated sense of self from the discrete behavioral states which predominate in infancy" until these discrete states "eventually coalesce, unify, and present as a continuous self across differing situations."

Putnam posits that an abusive parent-child relationship disrupts the child's attainment of self-control of its behavioral states. The child creates varying behavioral states which respond to the requirements of the abusive adult, and the continuing trauma interferes with the child's ability to integrate and consolidate self and behavior. This may be the behavioral mechanism behind the discrete dissociative states seen in DID.

Forrest's neurodevelopmental approach

Kelly A. Forrest builds on Putnam's model in her theory of the neurobiological basis of dissociative identity disorder. She brings together the neurosciences, cognitive psychology and developmental psychopathology.

Orbitalfrontal cortex Previous research posits that the OFC is responsible for the ability of healthy adult humans to be conscious of and have mental representations of their past, present and future subjective experiences. Since DID consists of the amnesia for, or splitting off of, subjective experiences, Forrest theorizes that the OFC is the locus of this fragmented consciousness, or dissociative states.
	The OFC has the inhibitory function of controlling distracting information that would impede current goal-directed organization of behavior. This function is similar to the ability to focus attention and exclude distractions. Through its reciprocal connections with sensory association cortices and subcortical drive and affective integration centers, the OFC monitors internal and external environments. It is responsible for attachment processes, autonomic regulation, "inhibition of subcortical drives, regulation of body states and regulation of autonomic responses to affective environmental cues."
The primary neurotransmitters affecting the OFC are dopamine and norepinephrine, which are responsible for emotion, attention, movement and visceral functioning. The dopaminergic limbic forebrain-midbrain circuit interacts with the OFC in instigation of movement toward emotionally significant stimuli, control of motivational reward effects, enjoyment of social interactions, and "the delayed response function." The delayed response function permits humans to respond based on past depictions rather than current environment. The function of norepinephrine may be to "facilitate the integrative processing of somatosensory information." There is a critical period in the development and myelination of the OFC between 10 and 12 months of age which is the same time when attachment patterns are able to be reliably measured. Myelination is complete at around age 12, with a rapid increase between ages 6-9, which is thought to explain the cognitive gains over these ages. The OFC is right-hemisphere dominant, responsible for "processing, expressing, and regulating emotional information and behavior."

Development of emotion regulation The OFC is important in temporal organization of behavior and emotion regulation. It "monitors and autoregulates the duration, frequency, and intensity" of positive and negative affect states. This facilitates humans' ability to recuperate from disturbances of affective state and experience continuity of self.
The developing OFC is affected by the relationship with the caregiver to impart internal representations it needs for regulating emotions. Young infants adjust their affective displays in response to their caregivers' affective displays. While infants can produce behaviors such as turning away from or toward their caregivers, and some self-soothing behaviors, development depends on the caregiver's responsiveness to their behaviors.
It is through these interactions that the resulting levels of neurotransmitters cause pruning of synapses after their initial overproduction, developing the corticolimbic circuits. Insecure attachment patterns result in an OFC that "cannot adaptively shift between internal states in response to emotional stresses." This results in a child who is unable to shift affective states appropriately in response to differing environmental contexts. Disorganized attachment patterns occur in response to maltreatment. These patterns are "characterized by sequential displays of contradictory behavior patterns, incomplete or interrupted movements and expressions, stilling or freezing behaviors, or direct indices of confusion." This contradictory behavior results from discontinuity in treatment of the child by the caregiver.

Development of the self

The Cognition Model describes cognition as "the combined ongoing activities of projecting, assimilating, accommodating, and dissociating." A child's initial demonstrations of its internal world are dependent on its interactions with its contexts, formed by its relation to its caregiver. Usually, by around 12 months the child has a stable concept of attachment. From that base, the child can start to move toward organization that is less context dependent. The child starts to be able to anticipate interactions and modify its behaviors in view of that. The infant's varied concepts of self and self-in-relation begin to coalesce into the child's more integrated and complex self-concept. This process depends on some consistency in the child's concepts of self over varying contexts.

Neurologically, the various self concepts are mediated by different neural networks. Integration into a more global self-concept would depend on overlapping activation of these networks. In the absence of consistent and predictable interactions with the caregiver, capacity for this integration is reduced. Dissociative identity disorder is a response, not to the inability to differentiate the internal from the external world, but from the inability of the OFC to integrate the separate neural networks corresponding to the different self concepts developed in relation to contradictory demands by the caregiver into overlapping neuronal connections that would enable the child to produce a global self concept over varying conditions. The inhibitory function of the OFC, which normally functions to reduce distractions in order to respond to the current context, in the case of DID functions prevent integration over varying contexts.

Experience-dependent neural reorganization

Many studies have supported experience-dependent plasticity of developing neural networks. Forrest contends that relatively autonomous neural networks represent various self concepts which must be incorporated to produce a unified global self concept.

Proposed "Orbitalfrontal Model" of DID This model posits that the OFC produces dissociated states by its function of protective inhibition in temporal organization of behavior. "[In] abusive environments when the [self or self-in-relation] concepts are sufficiently contradictory such that their integration would disorganize immediate goal-directed behaviors, the developing OFC inhibits the integration into the current projection of any conflicting [self] or [self-in-relation] concept when it arises." The OFC prioritizes immediate context over integrated context-independent organization. This expands on Putnam's discrete states model of DID.
Children with disorganized attachment patterns (a result of maltreatment) who develop DID, experienced neural development in a context of severe, chronic abuse. The child lives in a world that is unpredictable, with inconsistent responses from its caregiver(s), while the child's goal is to maintain attachment to its caregivers for the sake of survival.
The OFC cannot bias toward sympathetic nervous system high arousal or parasympathetic nervous system low arousal states because the abusive adult may demand organized behaviors from the child, while the child must at the same time remain hypervigilant due to the unpredictability of caregiver behaviors toward the child. In response, the OFC organizes behavior based on immediate context and inhibits integration of self concepts over time. The contradictory demands of the caregiver results in contradictory self concepts which operate autonomously in response to immediate demands. The dissociative amnesia between states results from the multiple, context-dependent, contradictory self concepts isolated by the OFC, through inhibition of posterior cortical areas. The lateral inhibition between neural networks results in amnesia which is context-specific. Forrest also theorizes that the process of fusion and integration of alter personalities during therapy is a result of "sufficient contiguity of dyadic input" to produce "overlap between neural networks containing conflicting [self] concepts."
Source: Forrest, Kelly A. (2001). Toward an etiology of dissociative identity disorder: a neurodevelopmental approach. Consciousness and Cognition, 10, 259-293.

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