Thursday, July 21, 2011

Borderline Personality Disorder, Impulsivity, and the Orbitofrontal Cortex



Yeah it’s a mouthful, I know. Since I’ve been talking about impulsive behavior I thought I’d take a look into one potential neurological explanation for impulsivity in Borderline Personality Disorder. Specifically this article focuses on the Orbitofrontal Cortex as a main cause for impulsive behavior.

It was a really well designed study that compared people with BPD to those with legions on the orbitofrontal cortex (damaged OFC), legions in other regions of the brain, and to healthy individuals. They subjected each group to various questionnaires and tests and produced an array of fascinating data which I will attempt to share concisely. So let’s begin shall we.


The goal of this study was to determine if certain aspects of BPD, in particular impulsive behavior, are associated with orbitofrontal cortex dysfunction since this has been associated with disinhibited or socially inappropriate behavior and emotional irregularities; all common features of BPD.

There were many similarities but also some significant differences. However these differences came in areas that were looking to draw conclusions in other areas of the Big 5 personality traits: openness, conscientiousness, extraversion, agreeableness, and neuroticism. This leads to the conclusion that many behaviors may be due to other brain regions, however, since impulsive activity was so similar in both groups it supports the fact that impulsive behavior may be linked to the orbitofrontal cortex.


What are some of the findings?

Similarities:
-        -   Personality: Significantly more impulsive.
-          - Behavioral Impulsivity: More behaviorally impulsive.  
-          - Time Production:  Produced significantly less time than the other two groups
-          - Impaired openness to new experience
-          - Subjective anger was higher and subjective happiness was lower

Differences:
-         -  BPD patients were significantly less extraverted and conscientious, and more neurotic than the other groups.
-          - BPD patients had increased levels of sadness, anger, and fear    (<~~~~~ Totally darksiders I don’t care what anyone says).
-         -  OFC groups reported a greater overestimation of time passing – indicating a faster subjective sense of time.
-          - OFC patients were more insensitive to reward

So what does this all mean? There was significant evidence that both groups were more impulsive as assessed with both behavioral and self-report measures. Since patients with OFC lesions and patients with BPD both performed similarly on tests that indicated more impulsivity and reported more inappropriate behaviors, more BPD traits, more anger, and less happiness than subjects in both of the comparison groups,it can be assumed that there is a connection in these areas. The tests also indicated they were less open to experience and have faster perceptions of time. These findings suggest that the orbitofrontal cortex functions may be related to these aspects of BPD but not to other BPD traits (such as levels of extraversion, conscientiousness, neuroticisms, and emotion).   Therefore it concludes that impulsive behavior could be related to orbitofrontal cortex function.

One thing I found interesting was the time studies. Patients with BPD and OFC lesions both had significantly lower time latencies on behavioral impulsivity tasks.  This result may be related to a desire to complete a task fast, combined with a lack of sensitivity to punishment (OFC lesions) and perhaps with the desire for the reward of finishing sooner (BPD). So, since those with BPD are more emotionally receptive to reward we are likely to rush into something in anticipation of gaining the end benefit. Both groups also produced less time than the other groups. A common cause could be a higher level of frustration in waiting for time to elapse. This study supports evidence that impulsivity and time perception are related. “The frustration in waiting and/or the faster cognitive tempo that may cause patients with orbitofrontal cortex lesions and patients with BPD to under produce time may also be related to some of the inappropriate social and emotional behaviors they display.”

However this study also found that patients with BPD were more neurotic, less extraverted and less conscientious than all other groups. Since the OFC legion group was similar to the other groups this shows that these areas are not related to the orbitofrontal cortex region. Other areas that are probably unrelated to the orbitofrontal cortex region are: higher levels of emotionality. One of the studies showed that an increased sensitivity to punishment might make patients with BPD more emotional, and the higher level of emotionality might then contribute to impulsive behavior.

This study was very well rounded in it does support exactly what it set out to prove, by both demonstrating direct correlations to impulsive behavior and by ruling out behavior that is not associated with that area of the brain. It goes on to say, “Our findings relate well to the hypothesis that the amygdale and orbitofrontal cortex act as part of an integrated neural system, as well as alone, in guiding decision making and adaptive response{s}. Patients with BPD have some deficits that can be related to the functions performed by the orbitofrontal cortex. These deficits might be related to smaller volume of the orbitofrontal cortext or to lower levels of activity in the orbitofrontal cortex.”

Fascinating. I’ve been meaning to take a look at more neurological and biogenetic causes for Borderline Personality Disorder for quite a while now. I think this is an interesting start, if not a bit dry. I hope it was informative at least. 

2 comments:

  1. very interesting. and people sometimes say "just snap out of it." right.

    ReplyDelete
  2. Heh. Sometimes people can be very ignorant.

    ReplyDelete

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