Limbic abnormalities in affective processing by criminal psychopaths as revealed by functional magnetic resonance imaging.By: Kent A Kiehl, Andra M Smith, Robert D Hare, Adrianna Mendrek, Bruce B Forster, Johann Brink, Peter F Liddle.

Presented by: Richard Rigby

-Psychopaths are characterized by a deficit in processing affective material* which can lead to symptoms such as: -superficiality

-lack of empathy, guilt, or remorse

-failure to experience or appreciate the significance of emotional stimulus *Affective material: something that elicits an emotional response.

Who are Psychopaths?

-1% of the general population are psychopaths-15-25% of the prison population are psychopaths

-Using SPECT it was found that psychopaths show greater bilateral activation for affective stimuli in the temporofrontal cortex.

-This suggests psychopaths require more activation in areas outside the limbic system to evaluate effective stimuli -Many other structures have been suggested to cause psychopathy, yet little was known about their involvement

Previous Research

Using an fMRI (1.5 T) to measure emotional processes in the brain activated by an affective memory task.

Purpose

Participants:-Criminals from a maximum security prison in Abbotsford BC

-Criminal psychopaths (n=8) -Criminal non-psychopaths (n=8)

-Healthy participants from general population (n=8)-All participants were controlled to have no significant difference in:

-Years of substance abuse -Age-Parental socioeconomic status-IQ

-The Hare Psychopathy Checklist-Revised assessed psychopathy

Participants

-Affective (lack of empathy)

-Interpersonal (manipulative)

-Antisocial (keep going back to jail)

-Lifestyle (craves high stimulation, unreasonable goals)

PCL-R

4 Dimensions:

Procedure

- Encoding: subjects memorized 12 words shown on a screen one at a time (0.5s to view word, 1.5 in between)

chaircarfishtoaster

Procedure

- Rehearsal: participants were told to rehearse words

rehearse

Procedure

- Recognition: 12 words presented, participants were asked if the word was present in the first sequence (2s to view word, 0.5s in between) .

chaircatboxtoaster

Procedure

-Repeated 8 times-On half the trials all words were neutral (Ex. Chair)-The other half were negative words (Ex. Hate) which were used as an affective stimuli

hatekillpunchcry

Results

-Psychopaths showed less activation than non-psychopaths in response to the affective stimuli in:

-rostral and cuadal anterior cingulate

-posterior colingulate-left inferior frontal gyrus-right and left amygdala-ventral striatum-parahippocampal gyrus-bilateral anterior superior

temporal gyrus

Results

-Psychopaths showed less activation than non-psychopaths in response to the affective stimuli in:

-All are areas of the Limbic System or Frontal Lobe

Results

-Psychopaths showed greater activation outside the limbic system in response to affective stimuli:

-left anterior superior temporal gyrus

-left anterior inferior frontal gyrus-right inferior frontal gyrus

Discussion

-Psycopathy is a result of limbic system and frontal lobe abnormalities, which affect:

-The ability to process emotions (amygdala, ventral striatum, and hippocampal formation)

-Memories (amygdala, ventral striatum, and hippocampal formation)

-Fear of punishment (amygdala)

-Psychopaths use non-limbic regions more than non-psychopaths to process affective stimuli.

Discussion

-Limitations: -Small sample size-Substance abuse could have

altered results

Future experiments: -Different affected stimuli (faces)

My Opinion

Pros-Lots of previous research-They controlled confounds very well in their participants-They included brain images-Thorough explanation of results

Cons-The images weren’t great-Lots of complicated jargon about random effects analysis-Complicated large tables

References

Kiehl, K. A., et al (2001). Limbic abnormalities in affective processing by criminal psychopaths as revealed by functional magnetic resonance imaging. Bio Psychiatry, 50, 677-684.

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