Homozygous EXOSC3 c.395A>C Variants in Pontocerebellar Hypoplasia Type 1B: A Sibling Pair With Childhood Lethal Presentation and Literature Review.

Pontocerebellar hypoplasia type 1B (PCH1B) is an autosomal recessive neurodegenerative disorder that involves hypoplasia or atrophy of the cerebellum and pons. PCH1B is caused by mutations in EXOSC3, which encodes a subunit of the RNA exosome complex. The most frequently observed mutation in PCH1B patients is a c.395A>C (p.D132A) missense variant, for which the homozygous mutation typically results in milder symptoms compared to compound heterozygous mutations or homozygous mutations for other pathogenic variants. In the present study, we report on a sibling pair harboring homozygous EXOSC3 c.395A>C missense variants who deteriorated more rapidly than previously described. These cases expand the spectrum of clinical manifestations of PCH1B associated with this variant, highlighting the need for further research to determine predictive factors of PCH1B severity.

Generalization and False Memory in an Acquired Equivalence Paradigm: The Influence of Physical Resemblance Across Related Episodes.

The ability to make inferences about related experiences is an important function of memory that allows individuals to build generalizable knowledge. In some cases, however, making inferences may lead to false memories when individuals misremember inferred information as having been observed. One factor that is known to increase the prevalence of false memories is the physical resemblance between new and old information. The extent to which physical resemblance has parallel effects on generalization and memory for the source of inferred associations is not known. To investigate the parallels between memory generalization and false memories, we conducted three experiments using an acquired equivalence paradigm and manipulated physical resemblance between items that made up related experiences. The three experiments showed increased generalization for higher levels of resemblance. Recognition and source memory judgments revealed that high rates of generalization were not always accompanied by high rates of false memories. Thus, physical resemblance across episodes may promote generalization with or without a trade-off in terms of impeding memory specificity.