Lateral entorhinal cortex lesions impair odor-context associative memory in male rats.

Lateral entorhinal cortex (LEC) has been hypothesized to process nonspatial, item information that is combined with spatial information from medial entorhinal cortex to form episodic memories within the hippocampus. Recent studies, however, have demonstrated that LEC has a role in integrating features of episodic memory prior to the hippocampus. While the precise role of LEC is still unclear, anatomical studies show that LEC is ideally placed to be a hub integrating multisensory information. The current study tests whether the role of LEC in integrating information extends to long-term multimodal item-context associations. In Experiment 1, male rats were trained on a context-dependent odor discrimination task, where two different contexts served as the cue to the correct odor. Rats were pretrained on the task and then received either bilateral excitotoxic LEC or sham lesions. Following surgery, rats were tested on the previously learned odor-context associations. Control rats showed good memory for the previously learned association but rats with LEC lesions showed significantly impaired performance relative to both their own presurgery performance and to control rats. Experiment 2 went on to test whether impairments in Experiment 1 were the result of LEC lesions impairing either odor or context memory retention alone. Male rats were trained on simple odor and context discrimination tasks that did not require integration of features to solve. Following surgery, both LEC and control rats showed good memory for previously learned odors and contexts. These data show that LEC is critical for long-term odor-context associative memory.

Disambiguating past events: Accurate source memory for time and context depends on different retrieval processes.

Current animal models of episodic memory are usually based on demonstrating integrated memory for what happened, where it happened, and when an event took place. These models aim to capture the testable features of the definition of human episodic memory which stresses the temporal component of the memory as a unique piece of source information that allows us to disambiguate one memory from another. Recently though, it has been suggested that a more accurate model of human episodic memory would include contextual rather than temporal source information, as humans' memory for time is relatively poor. Here, two experiments were carried out investigating human memory for temporal and contextual source information, along with the underlying dual process retrieval processes, using an immersive virtual environment paired with a 'Remember-Know' memory task. Experiment 1 (n=28) showed that contextual information could only be retrieved accurately using recollection, while temporal information could be retrieved using either recollection or familiarity. Experiment 2 (n=24), which used a more difficult task, resulting in reduced item recognition rates and therefore less potential for contamination by ceiling effects, replicated the pattern of results from Experiment 1. Dual process theory predicts that it should only be possible to retrieve source context from an event using recollection, and our results are consistent with this prediction. That temporal information can be retrieved using familiarity alone suggests that it may be incorrect to view temporal context as analogous to other typically used source contexts. This latter finding supports the alternative proposal that time since presentation may simply be reflected in the strength of memory trace at retrieval - a measure ideally suited to trace strength interrogation using familiarity, as is typically conceptualised within the dual process framework.

Prevalence of back pain, its effect on functional ability and health-related quality of life in lower limb amputees secondary to trauma or tumour: a comparison across three levels of amputation.

BACKGROUND AND OBJECTIVES: The prevalence of back pain and its effect on function and health-related quality of life across three levels of lower limb amputation secondary to trauma or tumour was studied. STUDY DESIGN: Cross-sectional survey. METHODS: Forty-six lower limb amputees, aged 19-78 years, participated. The Roland Morris disability questionnaire (RMDQ) and the short form 36 health survey (SF-36) were used. RESULTS: Participants reported more back pain after amputation than before (p < 0.001). There was a significant association between back pain daily or several times/week and severe or moderate disability reporting on the RMDQ (p = 0.003). On the SF-36, the group as a whole scored significantly lower in health-related quality of life with regard to physical functioning, role physical, bodily pain, general health, social functioning and the physical component summary (PCS), and significantly higher in the mental component summary (MCS) compared to normative Swedish data. When all three levels of amputation were compared, no statistically significant differences were found in the RMDQ or SF-36 results. CONCLUSIONS: There was a high prevalence of back pain after amputation. Almost all participants having back pain daily or several times per week reported severe or moderate disability on the RMDQ. The group as a whole scored significantly lower for health-related quality of life in the PCS and significantly higher in the MCS compared to normative Swedish data. CLINICAL RELEVANCE: The high prevalence of back pain, and the significant association between back pain daily or several times per week and severe or moderate disability on the RMDQ, and the negative correlation between RMDQ and SF-36, may have clinical relevance with regard to rehabilitation and follow-up of lower limb amputation.

The ScanHip total hip arthroplasty: radiographic assessment of 72 hips after 10 years.

We analyzed the radiographic and clinical outcome of the ScanHip total hip arthroplasty in 70 patients after 10 years. The Swedish National Hip Register, in which the end-point of the survival analysis is defined as revisions, reported a 10-year survival rate of 94% with the ScanHip, but in the present series 13% of the femoral stems and 29% of the sockets met the criteria for aseptic loosening. Focal osteolysis was found around 8 sockets (11%) and 23 stems (32%) and had occurred significantly oftener around loose sockets, but not around femoral stems. Linear polyethylene wear was significantly increased in loose sockets, but no relationship was noted between polyethylene wear and stem loosening or was there a correlation between clinical symptoms or patients' satisfaction and component loosening. Therefore precise serial long-term radiographic follow-up is the only satisfactory method for detecting aseptic loosening of total hip arthroplasty. It gives the surgeon more detailed information about each case than survival analysis alone.