Agnosia for bird calls

Abstract

The cognitive organisation of nonverbal auditory knowledge remains poorly defined. Deficits of environmental sound as well as word and visual object knowledge are well-recognised in semantic dementia. However, it is unclear how auditory cognition breaks down in this disorder and how this relates to deficits in other knowledge modalities. We had the opportunity to study a patient with a typical syndrome of semantic dementia who had extensive premorbid knowledge of birds, allowing us to assess the impact of the disease on the processing of auditory in relation to visual and verbal attributes of this specific knowledge category. We designed a novel neuropsychological test to probe knowledge of particular avian characteristics (size, behaviour [migratory or nonmigratory], habitat [whether or not primarily water-dwelling]) in the nonverbal auditory, visual and verbal modalities, based on a uniform two-alternative-forced-choice procedure. The patient's performance was compared to healthy older individuals of similar birding experience. We further compared his performance on this test of bird knowledge with his knowledge of familiar human voices and faces. Relative to healthy birder controls, the patient showed marked deficits of bird call and bird name knowledge but relatively preserved knowledge of avian visual attributes and retained knowledge of human voices and faces. In both the auditory and visual modalities, his knowledge of the avian characteristics of size and behaviour was intact whereas his knowledge of the associated characteristic of habitat was deficient. This case provides further evidence that nonverbal auditory knowledge has a fractionated organisation that can be differentially targeted in semantic dementia.

Auditory Categorization of Man-Made Sounds Versus Natural Sounds by Means of MEG Functional Brain Connectivity

“…Furthermore, the functional connectivity maps showed that within the man-made category, there might be “key” connections for Artificial-versus-Natural relative to Musical-versus-Natural , even though the nodes remained the same for both comparisons. This could also explain cases of semantic impairments, where patients are impaired in a very specific category, while the remaining categories within the same domain are spared (McCarthy and Warrington, 2016; Muhammed et al, 2018). Therefore, it seems very probable that the perception of auditory objects relies on a large-scale distributed system, which follows distinct neuronal pathways, dissociated on the basis of the weight that each node has in the network.…”

Avian agnosia: A window into auditory semantics

“…First, Omar et al (2010) documented a professional trumpeter with SD, who retained the ability to recognise musical notation but showed an impairment in auditory music knowledge. Second, Muhammed et al (2018) reported on BA, a case of SD who had premorbid expertise in the domain of bird knowledge. Muhammed et al (2018) tested BA's knowledge of avian characteristics (size, behaviour and habitat) in the verbal, visual and auditory modalities.…”

“…Second, Muhammed et al (2018) reported on BA, a case of SD who had premorbid expertise in the domain of bird knowledge. Muhammed et al (2018) tested BA's knowledge of avian characteristics (size, behaviour and habitat) in the verbal, visual and auditory modalities. Relative to the performance of three healthy bird experts of a similar age, BA had an impairment in verbal and auditory bird knowledge but relatively preserved knowledge of avian visual attributes.…”

“…For both auditory and visual stimuli, BA had unimpaired knowledge of size and migratory behaviour and impaired knowledge of habitat, suggesting that the dissociation between auditory and visual knowledge was less than clear cut. Crucially, in neither the study by Omar et al (2010) or Muhammed et al (2018) was a comparison made between knowledge of auditory objects from comparable expert vs. non-expert categories. Although Muhammed et al (2018) compared BA's knowledge of birds and famous people, as the authors acknowledged, it was not possible to draw meaningful comparisons between performance on these tasks, as there were important differences in task requirements and these categories require different levels of discrimination.…”

“…Crucially, in neither the study by Omar et al (2010) or Muhammed et al (2018) was a comparison made between knowledge of auditory objects from comparable expert vs. non-expert categories. Although Muhammed et al (2018) compared BA's knowledge of birds and famous people, as the authors acknowledged, it was not possible to draw meaningful comparisons between performance on these tasks, as there were important differences in task requirements and these categories require different levels of discrimination. There are two plausible interpretations that could explain the difference between performance in visual vs. auditory knowledge.…”