possible mechanisms

In the context of fear conditioning Foa and Kozak (1986) draw upon Lang’s concepts (1977, 1979, 1985) to describe emotional processing in terms of fear networks. The fear network incorporates cognitive, sensory and affective information. Activation of the fear network by a triggering stimulus causes information in the network to enter conscious awareness. They hypothesise that successful emotional processing can only occur by integrating the information in the fear network with existing memory structures. They propose that there are two key elements to this process:

1. activation of the fear network so that it becomes accessible through the presentation of fear-relevant information

2. presentation of fear incompatible information

Other theorists have also suggested than a fundamental component of emotional processing may involve some form of restructuring of emotional information.

“This process requires both the activation of the existing emotion schemas and the generation of new information with which to reorganise the existing emotional processing network”. (pp. 265, Greenberg & Safran, 1987)

The idea that memories can be activated and altered by the addition of incompatible information is inconsistent with recent findings from fear conditioning in animal studies. These studies suggest that old memories are indelible and that fear reactions are inhibited by the creation of new memories rather than being altered by them (LeDoux, 1993, 1998).

It has been argued that associative network models based on a single representational format may be too simplistic to capture complex clinical phenomena (Brewin & Holmes, 2003; Teasdale, 1999). These difficulties can be overcome by multi-level models of cognition and emotion involving different representational formats and types of code (Brewin & Holmes, 2003). Such models may provide further insights into possible underlying mechanisms of emotional processing. Theorists from a variety of orientations have tended to converge in postulating two emotional (memory) processing systems. There is considerable conceptual overlap in their formulations:

an abstract, schematic, associative and implicit system that has connections with bodily response systems. This mode involves fast and automatic processes such as priming and spreading activation. It often involves large numbers of memories in parallel. It is not wholly dependent on verbal information – visual, kinaesthetic or other cues could provide the basis for priming or activating an emotional memory.

an abstract propositional ‘rational’ system that is analytical, reflective, logical and relies on high level executive functions. It is primarily based on verbally accessible semantic information.

Some examples of such models are presented in the table below:

	Names given to the two systems
Leventhal’s Perceptual Motor Theory (1979)	Conceptual	Schematic
Teasdale’s Interacting Cognitive Subsystems Model (ICS) (1999)	Propositional	Implicational
Epstein’s Cognitive Experiential Self Theory (CEST) (1994)	Rational	Experiential
Bucci’s Multiple Code Theory (1997)	Symbolic	Subsymbolic
Brewin’s Dual Representation Theory (1996)	Verbally Accessible Memory (VAM)	Situationally Accessible Memory (SAM)

Recent neuroscientific findings are consistent with these multi-level conceptualisations. Le Doux (1998) has reviewed evidence suggesting that emotion networks have direct anatomical connections to both the neocortex and the amygdala. Events that are highly emotional are likely to be registered at both subcortical and cortical levels. The subcortical route is shorter and rapid whereas the cortical route is longer and slower. In the subcortical route sensory information goes from the thalamus directly to the amygdala. In the cortical route information is sent from the thalamus to both the cortex and hippocampus and is then projected to the amygdala. As noted by Samilov & Goldfried, (2000) these recent findings support a qualitative distinction between cortically based and subcortical levels of information processing. They imply that not all emotional responses are mediated cortically; rather, some may by initiated without any cognitive participation:

“Emotional responses can occur without the involvement of the higher processing systems of the brain, systems believed to be involved in thinking, reasoning, and consciousness” (LeDoux, 1998, pp. 161)

In the context of PTSD it has been proposed that an important component of emotional processing may involve the transfer of aversive memories from an uncontrolled, somato-sensory and affective memory mode to a more controlled, verbal and conceptual memory mode (Gidron, Duncan, Lazar, Biderman, Tandeter, & Shvartzman, 2002). Likewise, Horowitz (1979, 1986; Horowitz, Markman, Stinson, Fridhandler & Ghannam, 1990) proposed that traumatic events are replayed in consciousness in an attempt to integrate the meanings of the event into pre-existing schemata. Excessive control of the flow of this information could lead to failure to emotionally process the event and the persistence of negative emotional reactions.

References

Dorset RDSU
Cornelia House Poole Hospital NHS Trust Longfleet Road Poole Dorset BH15 2JB
Email dawn.stevens@poole.nhs.uk