1 / 28

Schizophrenic Syndrome

Cellular, Behavioral, and Computational Investigations of Dopamine Modulation of Prefrontal Cortical Networks Jeremy Seamans. Schizophrenic Syndrome. Positive Symptoms (delusions, hallucinations, disorganized speech, and grossly disorganized or abnormal thinking and behavior)

talbot
Download Presentation

Schizophrenic Syndrome

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Cellular, Behavioral, and Computational Investigationsof Dopamine Modulation of Prefrontal Cortical Networks Jeremy Seamans

  2. Schizophrenic Syndrome • Positive Symptoms(delusions, hallucinations, disorganized speech, and grossly disorganized or abnormal thinking and behavior) • Negative Symptoms(affective flattening, alogia, and avolition, social withdrawl) • Cognitive Symptoms(distractability, loss of flexible control of behavior). “Cognitive impairment in schizophrenia is the core of the disorder.” -Elvevag & Goldberg 2000 “Long term prognosis for individuals with schizophrenia appears to be best predicted, not by the severity of positive symptoms, but the degree of cognitive impairment” -Lewis & Lieberman 2000

  3. Schizophrenic Syndrome=Attentional Syndrome As early as the 1900s Kraeplin noted that the more debilitating symptoms of schizophrenia, are disturbances in attention and cognition “Attentional deficits in schizophrenia may be a principal cause of various deficits in higher order cognitive functions...Distractability interferes with the organizational aspects of memory” -Kenny & Meltzer 1991 “Schizophrenic patients present deficits...which depend on the executive attention network.” -Fuentes 2001 • Cognitive Symptoms = Dysfunction ofexecutive attention (flexible control of behavior). • Positive Symptoms - Dysfunction of attention within thought/perception • Negative Symptoms - Dysfunction of emotional attention.

  4. The Prefrontal/Dopamine link • Altered release proteins, interneuron as well as altered dopamine receptor function in the prefrontal cortex (PFC) of schizophrenics. • Patients with PFC damage exhibit similar problems to schizophrenics • Schizophrenics are unable to activate PFC on cognitive tasks • This inactivity can be reversed by a dopamine agonist • D2 receptor affinity REQUIRED for antipsychotic efficacy while dopamine agonists can induce psychotic symptoms • Clozapine produces high levels of D2 occupancy in cortex (relative to striatum) while chronic treatment upregulates cortical D2 receptors and downregulates D1 receptors. • Clozapine and other antipsychotics upregulate cortical dopamine turnover. Therefore schizophrenics exhibit a dysfunction in PFC dopamine systems that can be reversed by antipsychotics

  5. How does dopamine regulate network representations in PFC? • Behavioral approach: What is dopamine doing functionally? • Electrophysiological approach: What are the mechanisms involved in this dopamine regulation? • Computational approach: How do the mechanisms relate to function?

  6. Behavioral analyses of dopamine regulation of PFC dependent cognitive processes

  7. Adapted from: Sawaguchi et al. (1986; 1988; 1990a,b)

  8. Dopamine regulation of PFC neurons:Physiological action of dopamine in vitro

  9. Summary of the Physiological Effects of Dopamine

  10. D1 receptor activation enhances evoked firing by shifting INAP activation

  11. D1 receptor activation increases NMDA EPSCs selectively

  12. Dopamine has bi-directional effects on IPSCs D2 D1

  13. D2-mediated reduction of IPSCs is blocked by a muscarinic acetylcholine antagonist (Atropine)

  14. Summary of the Physiological Effects of Dopamine

  15. Linking cellular mechanisms to the functions of dopamine in the PFC Computational Modeling (Daniel Durstewitz)

  16. Simulation of D1 effects leads to reduction in spontaneous but large enhancement in evoked “delay-period” activity

  17. Supervisors Anthony Phillips (UBC) Charles Yang (UBC, Lilly Research Labs. ) Natalia Gorelova (UBC) Terry Sejnowski (Salk Institute) Charles Stevens (Salk Institute) Collaborators Stan Floresco (UBC) Daniel Durstewitz (Salk Institute)

More Related