Memory and Executive Functions Subserving Judgments of Learning: Cognitive Reorganization After Traumatic Brain Injury.

We investigated relationships between psychometric measures of memory, executive functions (EFs), and task-based measures of Judgments of Learning (JOLs) in individuals with and without Traumatic Brain Injury (TBI), to study functional reorganization after TBI. We hypothesized that, in controls, accuracy of immediate JOLs would be associated with short-term memory and EFs (but not long-term memory, LTM), while accuracy of delayed JOLs would be associated primarily with LTM. We hypothesized that those with good recovery from TBI would demonstrate functional reorganization of the relationships between memory, EFs, and JOLs. Eighteen individuals with TBI and 18 matched controls completed eight neuropsychological tests of memory and EFs. They studied word-pairs, made immediate and delayed JOLs, and took a cued-recall test for the studied word-pairs. Stepwise regression and Lasso analyses generated a predictive model of JOL accuracy for each group. Accuracy of immediate JOLs in controls was predicted by short-term memory, inhibition, switching, and cognitive fluency, while accuracy of delayed JOLs was predicted by verbal recall. In individuals with TBI, inhibition predicted immediate JOL accuracy and switching predicted delayed JOL accuracy. Cognitive reorganization in those with good long-term recovery from TBI may account for the ability to make JOLs with accuracy similar to controls.

Identifying objects impairs knowledge of other objects: a relearning explanation for the neural repetition effect.

Different items in long-term knowledge are stored in the neocortex as partially overlapping representations that can be altered slightly with usage. This encoding scheme affords well-documented benefits, but potential costs have not been well explored. Here we use functional magnetic resonance imaging (fMRI), neurocomputational modeling, and electrophysiological measures to show that strengthening some visual object representations not only enhances the subsequent ability to identify those (repeated) objects-an effect long known as repetition priming-but also impairs the ability to identify other (non-repeated) objects-a new effect labeled antipriming. As a result, the non-repeated objects elicit increased neural activity likely for the purpose of reestablishing their previously weakened representations. These results suggest a novel reevaluation of the ubiquitously observed repetition effect on neural activity, and they indicate that maintenance relearning may be a crucial aspect of preserving overlapping neural representations of visual objects in long-term memory.

Phonation threshold pressure across the pitch range: preliminary test of a model.

This study sought to examine the specific relationship between phonation threshold pressure (PTP) and voice fundamental frequency (F(0)) across the pitch range. A published theoretical model of this relationship described a quadratic equation, with PTP increasing exponentially with F(0). Prospective data from eight adults with normal, untrained voices were collected. Subjects produced their quietest phonation at 10 randomly ordered pitches from 5% to 95% of their semitone pitch range at 10% intervals. Analysis included curve fitting for individual and group data, as well as comparisons to the previous model. The group data fit a quadratic function similar to that proposed previously, but the specific quadratic coefficient and constant values differed. Four of the individual subjects' data were best fit by quartic functions, two by quadratic functions, and one by a linear function. This preliminary study indicates that PTP may be minimal at a "comfortable" pitch rather than the lowest pitch tested, and that, for some individuals, PTP may be slightly elevated during the passaggio between modal and falsetto vocal registers. These data support the general form of the theoretical PTP-F(0) function for these speakers, and indicate the possibility of potential refinements to the model. Future studies with larger groups of male and female subjects across a wider age range may eventually reveal the specific nature of the function.

Implicit memory influences on metamemory during verbal learning after traumatic brain injury.

PURPOSE: Prior research has shown that individuals with traumatic brain injury (TBI) may be overconfident in their judgments of learning (JOLs; online measures of self-monitoring of learning and memory). JOLs had been presumed to be driven by explicit processes, but recent research has also revealed implicit memory involvement. Given that implicit learning mechanisms are often intact in those with TBI, the purpose of this study was to investigate whether priming and antipriming of immediate and delayed JOLs in individuals with TBI might affect their overconfidence. METHOD: A standard 3-field masked priming paradigm was combined with a paired-associate learning task with JOLs and administered to individuals with TBI and matched controls (18 per group). In each trial, a subliminal masked stimulus was immediately followed by supraliminal presentation of a word pair for study; participants also made immediate and delayed JOLs, with cued-recall testing 10 min after study and judgment. RESULTS: Antipriming significantly lowered JOLs and overconfidence for both groups, whereas delaying JOLs significantly improved recall for both groups. CONCLUSIONS: The results suggest that JOLs may be influenced by subliminal implicit memory. Clinical implications include the possible use of antipriming to reduce overconfidence after brain injury and delaying JOLs to improve recall.