Sourcing high tissue quality brains from deceased wild primates with known socio‐ecology

Abstract

1. The selection pressures that drove dramatic encephalisation processes through the mammal lineage remain elusive, as does knowledge of brain structure reorganisation through this process. In particular, considerable structural brain changes are present across the primate lineage, culminating in the complex human brain that allows for unique behaviours such as language and sophisticated tool use. To understand this evolution, a diverse sample set of humans' closest relatives with varying socio-ecologies is needed. However, current brain banks predominantly curate brains from primates that died in zoological gardens. We try to address this gap by establishing a field pipeline mitigating the challenges associated with brain extractions of wild primates in their natural habitat.

Brain structure and function: a multidisciplinary pipeline to study hominoid brain evolution

“…Partners from the NHP Brain Network, in collaboration with the experts from the EBC consortium, extract brains after unavoidable death by following procedures which ensure exceptionally high-quality MRI and histological data, with tissue quality validation demonstrated ( Gräßle et al, 2023 ). Collecting post mortem brains from apes in a captive setting is already challenging, 1 but collecting brains from wild primates with tissue quality suitable for high-end neuroimaging has rarely been achieved beforehand ( Sherwood et al, 2004 ).…”

“…In-toto extracted, structural intact brains exhibiting preserved cellular architecture pose the prerequisite for obtaining meaningful data via state-of-the-art imaging techniques as applied within the project’s framework. We successfully implemented an extraction and fixation protocol across collaborative sites resulting in high-tissue quality specimens from deceased apes regardless of their origin—including zoo-housed and wild roaming individuals (for a detailed description please view, Gräßle et al, 2023 ). In brief, brain removal is attempted as soon as possible following the individual’s death as post mortem lytic processes progressively deteriorate tissue integrity.…”

“…Thus far only first results from units early in the pipeline are available and published. These are behavioral data ( Kopp et al, 2021 ; Girard-Buttoz et al, 2022a , b ; Grampp et al, 2023 ; Bortolato et al, 2023a , b ), data on brain extraction ( Gräßle et al, 2023 ) as well as first detailed neuroanatomical data on a chimpanzee’s brain ( Eichner et al, 2023 ). Results of later units in the pipeline inherently will only be available later.…”

B1+$$ {B}_1^{+} $$‐correction of magnetization transfer saturation maps optimized for 7T postmortem MRI of the brain

“…These brains were acquired from wild and captive deceased chimpanzees who died unexpectedly of causes not related to this study (see Table S1 for more information). The general preparation of the tissue is described in References 30‐32. postmortem interval before fixation varied from 1 to over 16 hours between brains (Table S1).…”

Striking pay dirt: Contemporary methods for studying animal sociality in the wild

“…Crucially, these tools may also allow investigation of how much of the diet of these wild animals is impacted by humans themselves: in a nutshell, the future might tell us how much our wild subjects have remained wild in their foods, despite being confronted with increasingly encroaching humans (Gruber et al, 2019; McLennan & Hockings, 2014). Gräßle et al (2023) take a radically different approach and also tackle the ‘ecological validity’ of their wild subjects, but this time, by looking at their brains. Much of our knowledge regarding cognitive processes in animals comes from captive subjects, who have been argued by some to be impoverished versions of their wild counterparts (Boesch, 2007).…”