Distributional semantic models (DSMs) specify learning mechanisms with which humans construct a deep representation of word meaning from statistical regularities in language. Despite their remarkable success at fitting human semantic data, virtually all DSMs may be classified as prototype models in that they try to construct a single representation for a word's meaning aggregated across contexts. This prototype representation conflates multiple meanings and senses of words into a center of tendency, often losing the subordinate senses of a word in favor of more frequent ones. We present an alternative instance-based DSM based on the classic MINERVA 2 multiple-trace model of episodic memory. The model stores a representation of each language instance in a corpus, and a word's meaning is constructed on-the-fly when presented with a retrieval cue. Across two experiments with homonyms in both an artificial and natural language corpus, we show how the instance-based model can naturally account for the subordinate meanings of words in appropriate context due to nonlinear activation over stored instances, but classic prototype DSMs cannot. The instance-based account suggests that meaning may not be something that is created during learning or stored per se, but may rather be an artifact of retrieval from an episodic memory store.

Introduction Buprenorphine in the treatment of opioid use disorder (OUD) has several benefits including better long-term treatment adherence (1) and is a safer option for many patients due to buprenorphine’s limited potential to cause respiratory depression (4). In comparison to standard buprenorphine induction, induction via micro-dosing does not require a period of withdrawal and dramatically shortens the time required to complete induction. Prior micro-dosing protocols using sublingual (SL) (7-10) and transdermal forms (11) have been reported. We present a case of buprenorphine induction using a novel inpatient intravenous micro-dosing 4-day protocol in a patient on methadone. Case Presentation A 62-year-old man with chronic obstructive pulmonary disease (COPD) on chronic methadone 80mg daily for OUD presented with respiratory failure and was diagnosed with opioid overdose. He was transitioned from a naloxone infusion to intravenous micro-doses of buprenorphine and low dose methadone without experiencing significant withdrawal, and he was discharged on buprenorphine/naloxone SL. Discussion This case demonstrates a successful and well tolerated buprenorphine induction without interruption of methadone treatment or precipitation of significant opioid withdrawal. To the best of our knowledge, this is the first report describing micro-induction with intravenous buprenorphine.

Impairments in category verbal fluency task (VFT) performance have been widely documented in psychosis. These deficits may be due to disturbed “cognitive foraging” in semantic space, in terms of altered salience of cues that influence individuals to search locally within a subcategory of semantically related responses (“clustering”) or globally between subcategories (“switching”). To test this, we conducted a study in which individuals with schizophrenia (n = 21), schizotypal personality traits (n = 25), and healthy controls (n = 40) performed VFT with “animals” as the category. Distributional semantic model Word2Vec computed cosine-based similarities between words according to their statistical usage in a large text corpus. We then applied a validated foraging-based search model to these similarity values to obtain salience indices of frequency-based global search cues and similarity-based local cues. Analyses examined whether diagnosis predicted VFT performance, search strategies, cue salience, and the time taken to switch between vs search within clusters. Compared to control and schizotypal groups, individuals with schizophrenia produced fewer words, switched less, and exhibited higher global cue salience, indicating a selection of more common words when switching to new clusters. Global cue salience negatively associated with vocabulary ability in controls and processing speed in schizophrenia. Lastly, individuals with schizophrenia took a similar amount of time to switch to new clusters compared to control and schizotypal groups but took longer to transition between words within clusters. Findings of altered local exploitation and global exploration through semantic memory provide preliminary evidence of aberrant cognitive foraging in schizophrenia.

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Figure 9 in the original version of the article contained an error. The corrected Fig. 9 is presented below. Conclusions from the Instance Theory of Semantics (ITS) are preserved. However, conclusions from LSA and BEAGLE are not. Like the ITS, both LSA and BEAGLE disambiguated the meaning of a homonym when conditionalized on a disambiguating prime, whether the homonym does or does not have a dominant sense.The online version of the original article can be found at https://doi.