Schizophrenia is a neuropsychological disorder in which the neural systems which regulate attention allocation, primarily the dorsolateral prefrontal cortex, are

dysfunctional, resulting in deficient gating of attention to irrelevant inputs from the environment. This sensory processing dysfunction hinders goal-directed behaviour to the extent that the subsequent cognitive deficits of schizophrenia prevent many chronic patients from leading normal lives. It is the onus of neuroscience to understand the nature of deficits induced by the disorder, thus providing target mechanisms for remediation of those deficits in patients. To accomplish this, manipulations in rats with relevance to schizophrenia are examined in assays with translation to human neurobiology and behaviour. In this thesis, three manipulations with relevance to schizophrenia, were examined for attentional regulation in the attentional set-shifting task, and similar assays, to determine how different forms of schizophrenia-related pathology influence attentional regulation and behavioural flexibility.

The foremost findings of the experiments herein were that manipulations inducing schizophrenia-related neurobiology, resulted in impaired performance in

extradimensional set-shifting and reversal learning. These deficits were found following: acute inhibition of the mPFC in adult rats, in adult rats who had been exposed to a glutamate receptor antagonist during the neonatal period of development, and/or in adult rats who had gestational disruption of neuron proliferation. Across all three manipulations, a clear behavioural pattern of deficient sensory gating, evidenced by responding to irrelevant stimuli during the set-shifting task was found.

These findings suggest that at the core of the cognitive deficits in schizophrenia is the 'loosening of associations' such that patients suffer the inability to regulate

attention, and limit sensory processing to relevant information. The subsequent aberrant learning about irrelevant information then impairs performance during goal-

directed behaviours.

11 Overview  - - - - - - - - - - - - - - - - - - - - - - - - -   2 

12 Schizophrenia genetics and neurochemistry  - - - - - - - - - - - - - -   3 

121 Dopamine  - - - - - - - - - - - - - - - - - - - - - - -   5 

123 Glutamate  - - - - - - - - - - - - - - - - - - - - - - -   7 

124 GABA  - - - - - - - - - - - - - - - - - - - - - - - -   9 

13 Schizophrenia neuroanatomy  - - - - - - - - - - - - - - - - - -   10 

14 Schizophrenia behavioural flexibility and attentional regulation  - - - - - - -   13 

141 Schizophrenia and the Wisconsin Card Sorting Test- - - - - - - - - -   14 

142 Schizophrenia and the Attentional Set-Shifting Task  - - - - - - - - -   17 

15 Tasks used to measure behavioural flexibility in rodents  - - - - - - - - -   21 

16 Thesis rationale  - - - - - - - - - - - - - - - - - - - - - -   25 

21 ASST protocol  - - - - - - - - - - - - - - - - - - - - - - -   28 

211 Apparatus  - - - - - - - - - - - - - - - - - - - - - - -   28 

212 Training - - - - - - - - - - - - - - - - - - - - - - -   28 

213 Standard 7-stage ASST testing  - - - - - - - - - - - - - - - -   29 

22 Histology - - - - - - - - - - - - - - - - - - - - - - - -   30 

23 Statistical analysis - - - - - - - - - - - - - - - - - - - - -   32 

231 Frequentist approach: Null hypothesis testing  - - - - - - - - - - -   32 

232 Probability approach: Bayesian analysis  - - - - - - - - - - - - -   32 

31 Introduction to acute manipulations to induce ‘schizophrenia-related’ behaviour in 

rodents  - - - - - - - - - - - - - - - - - - - - - - - - - -   42 

311 Adult sub-chronic/acute NMDA receptor antagonist manipulations  - - - -   42 

312 Stress-induced perturbations - - - - - - - - - - - - - - - -   44 

313 Lesion experiments  - - - - - - - - - - - - - - - - - - - -   45 

314 Inactivation of the mPFC via designer receptors exclusively activated by designer 

drugs (DREADDs)  - - - - - - - - - - - - - - - - - - - - - -   47 

32 Rationale  - - - - - - - - - - - - - - - - - - - - - - - -   48

33 Methods and materials  - - - - - - - - - - - - - - - - - - - -   49 

33 1 Animals - - - - - - - - - - - - - - - - - - - - - - -   49 

332 Pharmacogenetic manipulation  - - - - - - - - - - - - - - - -   49 

333 Behavioural Testing - - - - - - - - - - - - - - - - - - -   50 

34 Results  - - - - - - - - - - - - - - - - - - - - - - - - -   54 

341 mPFCin-rats have set-shifting deficits in the standard 7-stage ASST - - - - -   54 

342 Behavioural pattern analysis reveals increased irrelevant dimension responding in 

mPFCin-rats  - - - - - - - - - - - - - - - - - - - - - - - -   56 

343 mPFCin-rats attend to stimuli in the irrelevant dimension - - - - - - - -   58 

35 Discussion  - - - - - - - - - - - - - - - - - - - - - - - -   62 

351 Irrelevant dimension responding during set-shifting inducing enhanced learned 

irrelevance - - - - - - - - - - - - - - - - - - - - - - - -   62 

352 Model of neural mechanisms of the mPFC-inhibition on ASST performance - -   64 

353 Implications for theories of attention and associative learning  - - - - - -   70 

36 Histological Analysis of mPFC DREADDs - - - - - - - - - - - - - - -   73 

Rationale  - - - - - - - - - - - - - - - - - - - - - - - - -   73 

37 Methods and materials  - - - - - - - - - - - - - - - - - - - -   73 

38 Results  - - - - - - - - - - - - - - - - - - - - - - - - -   74 

381 All rats exhibited clear DREADDs expression within the mPFC - - - - - -   74 

382 DREADDs are trafficked throughout the projections of the infected mPFC neurons

 - - - - - - - - - - - - - - - - - - - - - - - - - - - -   75 

383 No difference in c-Fos immunoreactivity following clozapine-N-oxide 

administration  - - - - - - - - - - - - - - - - - - - - - - -   77 

39 Discussion  - - - - - - - - - - - - - - - - - - - - - - - -   80 

391 Analysis of DREADDs expression  - - - - - - - - - - - - - - -   80 

392 Infected projections are consistent with the pattern of mPFC neuronal projections

 - - - - - - - - - - - - - - - - - - - - - - - - - - - -   80 

393 Inhibitory DREADDs can be effective without reduction in activity at the cell body

 - - - - - - - - - - - - - - - - - - - - - - - - - - - -   81 

41 Introduction to neonatal-NMDAR antagonism rats  - - - - - - - - - - -   84 

411 Neurochemistry - - - - - - - - - - - - - - - - - - - - -   85 

412 Brain structural abnormalities  - - - - - - - - - - - - - - - -   87 

413 Schizophrenia-related innate behaviour in neonatal-NMDAR blockaded rats  - -   87

414 Schizophrenia-related attentional set-shifting behaviour in neonatal-PCP-treated 

rats  - - - - - - - - - - - - - - - - - - - - - - - - - -   89 

42 Rationale  - - - - - - - - - - - - - - - - - - - - - - - -   90 

43 Methods and materials  - - - - - - - - - - - - - - - - - - - -   90 

431 Animals - - - - - - - - - - - - - - - - - - - - - - -   90 

432 Behavioural Testing - - - - - - - - - - - - - - - - - - -   91 

44 Results  - - - - - - - - - - - - - - - - - - - - - - - - -   94 

441 Neonatal-PCP-treated rats show no clear deficits in the ASST  - - - - - -   94 

442 Neonatal-PCP-treated rats have an ED deficit in the ASST-MSS  - - - - - -   98 

443 Young neonatal-PCP-treated rats show deficits in the short delay novel object 

discrimination, however this deficit is not present in adult neonatal-PCP rats - - -   101 

444 Adult neonatal-PCP-treated rats show deficits in the 24 hour delay novel object 

discrimination - - - - - - - - - - - - - - - - - - - - - - -   102 

45 Discussion  - - - - - - - - - - - - - - - - - - - - - - - -   102 

451 Failure to replicate the ASST deficits in neonatal-PCP-treated rats - - - -   102 

452 The ASST-MSS task revealed an ED deficit in neonatal-PCP-treated rats  - - -   104 

453 Developmental period dependent effects in neonatal-PCP-treated rats in the 

novel object recognition task - - - - - - - - - - - - - - - - - -   106 

454 Reproducibility of set-shifting results  - - - - - - - - - - - - - -   107 

46 Histological analysis of neonatal-PCP-treated rats  - - - - - - - - - - -   110 

Rationale  - - - - - - - - - - - - - - - - - - - - - - - - -   110 

47 Methods and materials  - - - - - - - - - - - - - - - - - - -   110 

48 Results  - - - - - - - - - - - - - - - - - - - - - - - - -   110 

481 Neonatal-PCP-treated rats exhibit a deficit in weight gain and post-mortem brain 

weight - - - - - - - - - - - - - - - - - - - - - - - - -   110 

482 Neonatal-PCP-treated rats have less parvalbumin-expression within the mPFC    112 

491 Successful replication of neonatal-PCP induced anatomical disruption  - - -   114 

492 Role of the mPFC disruption in the novel object recognition deficits  - - - -   114 

51 Introduction to the MAM manipulation - - - - - - - - - - - - - -   117 

511 MAM-treated rats anatomical and histological abnormalities  - - - - - -   117 

512 Neurotransmitter & electrophysiological abnormalities in MAM-treated rats  -   119 

513 Innate and behavioural flexibility deficits in MAM-treated rats - - - - -   121 

514 MAM-based translational evidence for schizophrenia treatments  - - - - -   122 

52 Rationale  - - - - - - - - - - - - - - - - - - - - - - - -   123 

53 Methods and materials  - - - - - - - - - - - - - - - - - - -   125 

531 Animals - - - - - - - - - - - - - - - - - - - - - - -   125 

532 Baseline 7-Stage ASST testing  - - - - - - - - - - - - - - - -   125 

533 ORG49209 ASST testing  - - - - - - - - - - - - - - - - - -   126 

534 4-ID testing  - - - - - - - - - - - - - - - - - - - - - -   126 

54 Results  - - - - - - - - - - - - - - - - - - - - - - - - -   127 

541 MAM-treated rats have a deficit at REV 1 of the standard ASST- - - - -   127 

542 MAM-treated have increased evidence for irrelevant dimension-based responding

 - - - - - - - - - - - - - - - - - - - - - - - - - - -   128 

543 No evidence of a MAM-induced ED deficit in the 4 ID task  - - - - - - -   130 

544 ORG49209 effect on REV 1 performance in controls and MAM-treated rats -   131 

55 Discussion  - - - - - - - - - - - - - - - - - - - - - - - -   132 

551 Reversal learning impairment in MAM-treated rats - - - - - - - - -   132 

552 Irrelevant dimension responding and perseveration in MAM-treated rats  - -   132 

553 Protocol based explanations for failures to replicate  - - - - - - - - -   133 

554 ORG49209 failed to improve REV 1 performance in MAM-treated rats  - - -   134 

56 Histological analysis of MAM-treated rats  - - - - - - - - - - - - - -   135 

Rationale  - - - - - - - - - - - - - - - - - - - - - - - - -   135 

57 Methods and materials  - - - - - - - - - - - - - - - - - - -   135 

58 Results  - - - - - - - - - - - - - - - - - - - - - - - - -   136 

581 MAM-treated rats exhibit abnormal brain and body weights  - - - - - -   136 

582 Gross observation reveals schizophrenia-related anatomy in MAM-treated rats

 - - - - - - - - - - - - - - - - - - - - - - - - - - -   137 

583 Parvalbumin expression is altered in the hippocampus but not mPFC of MAM-

treated rats  - - - - - - - - - - - - - - - - - - - - - - -   141 

59 Discussion  - - - - - - - - - - - - - - - - - - - - - - - -   144 

591 Failure to replicate reduced parvalbumin expression within the PFC  - - - -   144 

592 MAM treatment primarily affects the hippocampus  - - - - - - - - -   145 

61 Experimental summary  - - - - - - - - - - - - - - - - - - -   149 

62 Reliability of acute versus developmental manipulations and the relevance to 

schizophrenia  - - - - - - - - - - - - - - - - - - - - - - - -   150 

63 Utility of the Bayesian analysis for characterisation of behavioural pattern - - -   152 

64 Modifications to the standard ASST allow exploration of additional phenomenon-   154

65 Relevance of findings for theories of attention  - - - - - - - - - - - -   155 

66 General Conclusion  - - - - - - - - - - - - - - - - - - - - -   158