Anteroventral thalamic nucleus: lesion effects on memory and cortico-limbic electrophysiology

Damage to the anterior thalamic nuclei (ATN) is associated with severe memory impairment in humans. What is unclear is how this damage affects electrophysiological activity within an extended hippocampal circuit for memory, of which the ATN is a key component. The current study provides a novel comparison of the electrophysiological activity of rats with lesions to the ATN and intact rats using two electrophysiological measures. These measure are peak power generated by each structure of interest, and the amount of signal amplitude covariance shared by structures, known as coherence. Data were recorded from four key neural memory structures (prefrontal cortex, hippocampus, retrosplenial cortex, and subiculum) during a behavioural paradigm in which rats were presented with novel or previously visited (repeat) arms in a radial arm maze. The current study found decreases in peak power within the sham group when entering repeat arms verses novel. There was also significantly reduced power in rats with ATN lesions compared to shams in the right hippocampus when entering novel arms, and in the right hippocampus and subiculum when entering repeat arms. While there were no significant between group differences in coherence, there was a reduction in coherence in shams when entering novel verses repeat arms in all structures analysed. Overall findings suggest that an intact ATN may play a regulatory role in electrophysiological activity across the extended hippocampal memory system

Quantification and Characterisation of Pre-Production Pellet Pollution in the Avon-Heathcote Estuary/Ihutai, Aotearoa-New Zealand

Plastic pollution is threatening aquatic ecosystems and wildlife. Understanding the characteristics and extent of plastic pollution is the first step towards improving management and therefore the environmental impacts. Pre-production pellets are used in the manufacture of a range of consumer items. The Avon–Heathcote Estuary/Ihutai in Aotearoa–New Zealand, an important wildlife habitat, was assessed for the presence and characteristics of pre-production pellets. Following a visual survey of the estuary’s perimeter to establish overall levels, seven accumulation hotspots were identified, and surveyed in more detail. The enumeration and characterisation of pellet colour, size, morphology, degree of weathering and polymer type was undertaken. A total of 3819 pellets were identified, with pellets present at all sites. The pellets were predominantly clear (86%), 3 mm in size (54%), cylindrical in shape (62%), showed moderate weathering (41%) and were made of low-density polyethylene (LDPE) (53%). Pellet abundance and characteristics varied between sites. Accumulation and abundance may be influenced by river inflows along which plastic manufacturers are located, weather conditions, locality to stormwater outlets and pellet characteristics. Pellet pollution is a notable problem in the Avon–Heathcote Estuary/Ihutai and it highlights the need to better understand the sources and improve best management practices