Relational memory function in schizophrenia: Electrophysiological evidence for early perceptual and late associative abnormalities.

We used event-related potentials (ERPs) to examine encoding and retrieval during episodic memory in people with schizophrenia (SZ) and biological relatives of SZ (SZr). To isolate contextual from item-specific aspects of memory, we employed the Relational and Item-Specific Encoding (RISE) task. Twenty two healthy controls (HCs), 22 SZ, and 19 SZr, encoded visual depictions of objects when displayed alone (item-specific) or in pairs (relational encoding), and were later tested on recognition of specific objects and whether pairs of objects had appeared together. An early posterior component (P2) during encoding predicted later recognition and was diminished in SZ. A late negative potential (LNP) over left frontal brain regions during recognition was larger for relationally encoded objects than new and item-specific encoded objects in HCs. This pattern was absent for SZ and SZr. Smaller P2 and LNP components were associated with greater self-reported cognitive-perceptual abnormalities. Early posterior brain responses likely relevant to perceptual functions supporting memory formation were diminished in schizophrenia. Late frontal electrophysiological responses associated with relational aspects of memory appear diminished in SZ and SZr, potentially reflecting the influence of genetic liability for schizophrenia on brain functions supporting episodic memory.

Auditory evoked brain potentials as markers of chronic effects of mild traumatic brain injury in mid-life.

OBJECTIVE: Auditory event-related potential (ERP) correlates of pre-dementia in late-life may also be sensitive to chronic effects of mild traumatic brain injury (mTBI) in mid-life. In addition to mTBI history, other clinical factors may also influence ERP measures of brain function. This study's objective was to evaluate the relationship between mTBI history, auditory ERP metrics, and common comorbidities. METHODS: ERPs elicited during an auditory target detection task, psychological symptoms, and hearing sensitivity were collected in 152 combat-exposed veterans and service members, as part of a prospective observational cohort study. Participants, with an average age of 43.6 years, were grouped according to positive (n = 110) or negative (n = 42) mTBI history. Positive histories were subcategorized into repetitive mTBI (3 + ) (n = 40) or non-repetitive (1-2) (n = 70). RESULTS: Positive history of mTBI was associated with reduced N200 amplitude to targets and novel distractors. In participants with repetitive mTBI compared to non-repetitive and no mTBI, P50 was larger in response to nontargets and N100 was smaller in response to nontargets and targets. Changes in N200 were mediated by depression and anxiety symptoms and hearing loss, with no evidence of a supplementary direct mTBI pathway. CONCLUSIONS: Auditory brain function differed between the positive and negative mTBI groups, especially for repetitive injury, which implicated more basic, early auditory processing than did any mTBI exposure. Symptoms of internalizing psychopathology (depression and anxiety) and hearing loss are implicated in mTBI's diminished brain responses to behaviorally relevant and novel stimuli. SIGNIFICANCE: A mid-life neurologic vulnerability conferred by mTBI, particularly repetitive mTBI, may be detectable using auditory brain potentials, and so auditory ERPs are a target for study of dementia risk in this population.