The function of chronic brain machine interfaces depends on stable electrical contact between neurons and electrodes. A key step in the development of interfaces is therefore to identify implant configurations that minimize adverse long-term tissue reactions. To this end, we here characterized the separate and combined effects of implant size and fixation mode at 6 and 12 weeks post implantation in rat (n = 24) cerebral cortex. Neurons and activated microglia and astrocytes were visualized using NeuN, ED1 and GFAP immunofluorescence microscopy, respectively. The contributions of individual experimental variables to the tissue response were quantified. Implants tethered to the skull caused larger tissue reactions than un-tethered implants. Small diameter (50 µm) implants elicited smaller tissue reactions and resulted in the survival of larger numbers of neurons than did large diameter (200 µm) implants. In addition, tethering resulted in an oval-shaped cavity, with a cross-section area larger than that of the implant itself, and in marked changes in morphology and organization of neurons in the region closest to the tissue interface. Most importantly, for implants that were both large diameter and tethered, glia activation was still ongoing 12 weeks after implantation, as indicated by an increase in GFAP staining between week 6 and 12, while this pattern was not observed for un-tethered, small diameter implants. Our findings therefore clearly indicate that the combined small diameter, un-tethered implants cause the smallest tissue reactions.
Secure base scripts (SBS) are thought of as the earliest, rudimentary mental representations of attachment, comprising temporally and causally related events occurring in interactions between children and their attachment figures. SBS have been studied in preschool children, adolescents and adults, but there is little research relating SBS to other attachment measures in middle childhood. Here, the Secure Base Script Test (SBST), a narrative-based measure of attachment scripts in middle childhood, was developed and evaluated. In two studies with 7-12-year-olds (total N = 261), high internal consistency, inter-rater reliability and discriminant validity was established. SBS knowledge was consistent across different contexts and relationships and converged strongly with security and coherence in representations assessed by the Friends and Family Interview and moderately with self-reported attachment security. Furthermore, SBS knowledge predicted children's capacity to respond to distress in an adaptive way. Our findings may be taken to provide some first evidence for generalized scripted attachment knowledge already in middle childhood.
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