The successor representation and temporal context.

The successor representation was introduced into reinforcement learning by Dayan ( 1993 ) as a means of facilitating generalization between states with similar successors. Although reinforcement learning in general has been used extensively as a model of psychological and neural processes, the psychological validity of the successor representation has yet to be explored. An interesting possibility is that the successor representation can be used not only for reinforcement learning but for episodic learning as well. Our main contribution is to show that a variant of the temporal context model (TCM; Howard & Kahana, 2002 ), an influential model of episodic memory, can be understood as directly estimating the successor representation using the temporal difference learning algorithm (Sutton & Barto, 1998 ). This insight leads to a generalization of TCM and new experimental predictions. In addition to casting a new normative light on TCM, this equivalence suggests a previously unexplored point of contact between different learning systems.

Distributed representations of dynamic facial expressions in the superior temporal sulcus.

Previous research on the superior temporal sulcus (STS) has shown that it responds more to facial expressions than to neutral faces. Here, we extend our understanding of the STS in two ways. First, using targeted high-resolution fMRI measurements of the lateral cortex and multivoxel pattern analysis, we show that the response to seven categories of dynamic facial expressions can be decoded in both the posterior STS (pSTS) and anterior STS (aSTS). We were also able to decode patterns corresponding to these expressions in the frontal operculum (FO), a structure that has also been shown to respond to facial expressions. Second, we measured the similarity structure of these representations and found that the similarity structure in the pSTS significantly correlated with the perceptual similarity structure of the expressions. This was the case regardless of whether we used pattern classification or more traditional correlation techniques to extract the neural similarity structure. These results suggest that distributed representations in the pSTS could underlie the perception of facial expressions.

Graded representations of emotional expressions in the left superior temporal sulcus.

Perceptual categorization is a fundamental cognitive process that gives meaning to an often graded sensory environment. Previous research has subdivided the visual pathway into posterior regions that processes the physical properties of a stimulus, and frontal regions that process more abstract properties such as category information. The superior temporal sulcus (STS) is known to be involved in face and emotion perception, but the nature of its processing remains unknown. Here, we used targeted fMRI measurements of the STS to investigate whether its representations of facial expressions are categorical or noncategorical. Multivoxel pattern analysis showed that even though subjects were performing a categorization task, the left STS contained graded, noncategorical representations. In the right STS, representations showed evidence for both stimulus-related gradations and a categorical boundary.

Distinctive encoding reduces the Jacoby-Whitehouse illusion.

We investigated the influence of distinctive encoding on the Jacoby and Whitehouse (1989) illusion. Subjects studied visually presented words that were associated with either an auditory presentation of the same word (nondistinctive encoding) or a picture of the object (distinctive encoding). In both conditions, words were visually presented on the recognition test, and half were preceded by brief repetition primes. Priming test items increased hits and false alarms in the auditory condition, demonstrating the Jacoby-Whitehouse illusion. This illusion was reduced in the picture condition. In order to test whether this distinctiveness effect was caused by a recollection-based response strategy (i.e., the distinctiveness heuristic), we minimized recollection-based responding by having subjects make speeded recognition decisions. Contrary to the distinctiveness heuristic hypothesis, speeded responding did not eliminate the distinctiveness effect on the Jacoby-Whitehouse illusion. Picture encoding may reduce this illusion via a shift in preretrieval orientation, as opposed to a postretrieval editing process.

Robot-assisted excision of seminal vesicle cyst associated with ipsilateral renal agenesis.

Seminal vesicle cysts associated with other genitourologic abnormalities are rare. We describe the first known robot-assisted excision of a cystic seminal vesicle associated with ipsilateral renal agenesis in a symptomatic pediatric patient. The patient was discharged home on postoperative day 1 and remains symptom free after 9 months' follow-up. Operative time, blood loss, and hospital stay were comparable to those of published series of conventional laparoscopy.

Aging can spare recollection-based retrieval monitoring: the importance of event distinctiveness.

The authors investigated two retrieval-monitoring processes. Subjects studied red words and pictures and then decided whether test words had been studied in red font (red word test) or as pictures (picture test). Memory confusions were lower on the picture test than on the red word test, implicating a distinctiveness heuristic. Memory confusions also were lower when study formats were mutually exclusive (the same item was never studied as both a red word and a picture), compared with a nonexclusive condition, implicating a recall-to-reject process. When the to-be-recollected events were pictures, older adults used each monitoring strategy as effectively as did younger adults.

Urothelial carcinoma recurrence in ileal orthotopic neobladder: urethrectomy and creation of ileal conduit.

A patient who had previously undergone radical cystoprostatectomy and ileal neobladder with the Studer technique presented with a recurrence of urothelial carcinoma in the neobladder and urethra. Surgical treatment consisted of resection of the neobladder, urethrectomy, and creation of an ileal conduit using a separately isolated segment of ileum. Pathologic analysis revealed high-grade urothelial carcinoma implants to the Studer pouch and urethra, with spread to the mesenteric lymph nodes draining the pouch. Intraluminal tumor cell seeding appears to be an important mechanism of metachronous transitional cell carcinoma recurrence in the urethra and ileal mucosa of a neobladder.

Neural mechanisms of expert skills in visual working memory.

Expertise can increase working memory (WM) performance, but the cognitive and neural mechanisms of these improvements remain unclear. Here, we used functional magnetic resonance imaging to assess the degree to which expertise acquisition is supported by tuning of occipitotemporal object representations and tuning of prefrontal and parietal networks that may support domain-specific WM skills. We trained subjects to become experts in a novel category of complex visual objects and examined brain activity while they performed a WM task with objects from the expert category and from an untrained category. Visual expertise training resulted in improved recognition of expert, compared with untrained objects, and this effect was eliminated in a behavioral experiment by stimulus inversion. These behavioral changes were accompanied by increased recruitment of bilateral dorsolateral prefrontal, posterior parietal, and occipitotemporal cortices during WM encoding and maintenance. Across subjects, behavioral measures of expertise reliably predicted increased activation during maintenance of expert objects in all three regions. These neural expertise effects could not be attributed to differences in low-level stimulus characteristics between the two categories, familiarity with features of expert-domain objects, or familiarity with the WM task. These results are consistent with the idea that visual expertise improves WM performance through tuning of occipitotemporal object representations and through development of lateral prefrontal and posterior parietal networks that mediate the application of domain-specific mnemonic skills.

Spurious hypocalcemia after gadodiamide-enhanced magnetic resonance imaging: a case report and review of the literature.

Gadolinium-enhanced magnetic resonance imaging is a diagnostic modality widely used in urologic practice. We report on a 54-year-old woman in whom a critically low serum calcium level was measured with standard colorimetric assay after gadodiamide-enhanced magnetic resonance imaging. The same phenomenon was noted in 2 other patients seen in our practice. Repeat serum calcium measurements performed several hours later were within normal limits. Commercially available gadolinium-based contrast agents might precipitate critically low serum calcium values when measured by standard colorimetric assay. Physician awareness of gadodiamide-induced spurious hypocalcemia might prevent unnecessary therapeutic interventions.