Neural regions underlying object and action naming: Complementary evidence from acute stroke and primary progressive aphasia

Abstract

Background: Naming impairment is commonly noted in individuals with aphasia. However, object naming receives more attention than action naming. Furthermore, most studies include participants with aphasia due to only one aetiology, commonly stroke. We developed a new assessment, the Hopkins Action Naming Assessment (HANA), to evaluate action naming impairments.

Aims: Our aims were to show that the HANA is a useful tool that can (1) identify action naming impairments and (2) be used to investigate the neural substrates underlying naming. We paired the HANA with the Boston Naming Test (BNT) to compare action and object naming. We considered participants with aphasia due to primary progressive aphasia (PPA) or acute left hemisphere stroke to provide a more comprehensive picture of brain-behaviour relationships critical for naming. Behaviourally, we hypothesised that there would be a double dissociation between object and action naming performance. Neuroanatomically, we hypothesised that different neural substrates would be implicated in object vs. action naming and that different lesion-deficit associations would be identified in participants with PPA vs. acute stroke.

Methods & procedures: Participants (N=138 with PPA, N=37 with acute stroke) completed the BNT and HANA. Behavioural performance was compared. A subset of participants (N=31 with PPA, N=37 with acute stroke) provided neuroimaging data. The whole brain was automatically segmented into regions of interest (ROIs). For participants with PPA, the image variables were the ROI volumes, normalised by the brain volume. For participants with acute stroke, the image variables were the percentage of each ROI affected by the lesion. The relationship between ROIs likely to be involved in naming performance was modelled with LASSO regression.

Outcomes & results: Behavioural results showed a double dissociation in performance: in each group, some participants displayed intact performance relative to healthy controls on actions but not objects and/or significantly better performance on actions than objects, while others showed the opposite pattern. These results support the need to assess both objects and actions when evaluating naming deficits. Neuroimaging results identified different regions associated with object vs. action naming, implicating overlapping but distinct networks of regions. Furthermore, results differed for participants with PPA vs. acute stroke, indicating that critical information may be missed when only one aetiology is considered.

Conclusions: Overall, the study provides a more comprehensive picture of the neural bases of naming, underscoring the importance of assessing both objects and actions and considering different aetiologies of damage. It demonstrates the utility of the HANA.

Keywords: action naming; aphasia; object naming; primary progressive aphasia; stroke.

Figure 1.

Behavioural results for participants with PPA (N=135) who completed both the HANA and BNT assessments. Performance on the BNT is shown on the y-axis (maximum score=30) and performance on the HANA is shown on the x-axis (maximum score=30). Dot fill colours represent different PPA variants (cyan=lvPPA; orange=nfvPPA; purple=svPPA; gray=unclassifiable). Dashed lines represent cut-offs for normal performance at z>−1.645 relative to controls, blue for the BNT and red for the HANA. Participants who showed intact performance on the BNT but impaired performance on the HANA relative to controls appear in the upper left; those who showed the opposite pattern are shown in the lower right. Participants who performed significantly better on the BNT than the HANA according to Fisher’s Exact Test are highlighted with blue squares. Participants who performed significantly better on the HANA than the BNT according to Fisher’s Exact Test are highlighted with red triangles.

Figure 2.

Behavioural results for participants with stroke (N=34) who completed both the HANA and BNT assessments. Performance on the BNT is shown on the y-axis (maximum score=30) and performance on the HANA is shown on the x-axis (maximum score=30). Dashed lines represent cut-offs for normal performance at z>−1.645 relative to controls, blue for the BNT and red for the HANA. Participants who showed intact performance on the BNT but impaired performance on the HANA relative to controls appear in the upper left; those who showed the opposite pattern are shown in the lower right. The participant who performed significantly better on the BNT than the HANA according to Fisher’s Exact Test is highlighted with a blue square. The participant who performed significantly better on the HANA than the BNT according to Fisher’s Exact Test is highlighted with a red triangle.

Figure 3.

Neuroimaging results for PPA. Regions in red were associated with action naming performance. Regions in blue were associated with object naming performance. Regions in magenta were associated with naming of both objects and actions. Slices are y=−73, −55. −36, −17, 2, and 21.

Figure 4.

Neuroimaging results for acute stroke. Regions in red were associated with action naming performance. Regions in blue were associated with object naming performance. Regions in magenta were associated with naming of both objects and actions. Slices are y=−73, −55. −36, −17, 2, and 21.