Impaired Naming of Famous Musical Melodies Is Associated With Left Temporal Polar Damage

Famous musical melodies, such as “Twinkle Twinkle Little Star” and “Old MacDonald,” are widely recognized in the western world. While the same musical melody may be represented in multiple ways, the melody itself is a unique, discrete entity. For example, at a birthday party when one person begins singing “Happy Birthday”, others join in, singing in whatever key was spontaneously chosen by the first singer. No matter what key this may be, the melody of “Happy Birthday” is easily and ubiquitously recognized. Similarly, melodies can be played on different instruments and despite the different sounds these make, the melodies tend to be quite recognizable. Semantically unique items are items that can be characterized by a unique identifier, or name (Gorno-Tempini & Price, 2001). Famous musical melodies are semantically unique items, because they are unique entities that are identified by a proper name, (e.g., “The Star Spangled Banner”). In this way, melodies are similar to other categories of unique entities, such as famous people and landmarks. While musical melodies are similar to famous people and landmarks in this regard, it is uncertain whether the category of famous musical melodies has the same neuroanatomical underpinnings as famous faces and landmarks. Importantly, famous faces and landmarks are both visual stimuli, while melodies are auditory. The neurobiology of this critical difference between these two classes of stimuli is not well understood. Previous research has frequently investigated the neuroanatomical underpinnings of recognition of famous musical melodies (Hailstone et al., 2009; Hsieh et al., 2011; Peretz et al., 1994; Platel et al., 2003; Steinke et al., 2001). In these studies, subjects have been asked to identify whether a melody is familiar or not, to continue humming the tune of the melody, or to pick the name of the melody from a group of names (in a multiple choice recognition format). Multiple brain regions have been implicated in the recognition of musical melodies, most frequently including regions in the bilateral temporal lobes. However, it is important to note that recognition of famous melodies is different from naming of melodies – the former refers to a set of semantic information that confers “knowing,” while the latter refers to a specific lexical entity that is a proper name. In the current study, we focus on the neuroanatomical basis of naming famous musical melodies, which has been far less studied than recognition. Only a few studies have investigated the neuroanatomical underpinnings of naming famous musical melodies. Ayotte and colleagues (2000) studied naming of famous musical melodies in patients who had undergone brain surgery for middle cerebral artery aneurysms. The authors found that, compared to normal comparison subjects, patients with left, but not right, hemisphere lesions were impaired at naming famous melodies. However, patients with lesions to the left hemisphere were also found to be impaired at recognizing famous melodies. Therefore, the authors were unable to specify a region that results in isolated deficits in naming famous melodies. Recently, Johnson and colleagues (2011) investigated naming of famous musical melodies, and found that patients with Alzheimer's disease, frontotemporal dementia, and semantic dementia were significantly impaired at naming famous musical melodies compared to normal comparison participants. Additionally, patients with semantic dementia performed significantly poorer than patients with Alzheimer's disease and frontotemporal dementia. However, as in the Ayotte et al. (2000) study, the semantic dementia patients who were impaired at naming famous melodies were also impaired at recognizing these melodies. Using voxel-based morphometry, the authors identified multiple regions in the left temporal lobe that correlated with performance on the famous melodies naming task. Taken together, previous research has provided some preliminary hints that the left temporal lobe is important for naming famous musical melodies. However, neuroanatomical regions responsible solely for naming of famous musical melodies have not been isolated; additionally, a clear mechanism for deficits in naming of famous melodies has not yet been found. Here, we propose that famous musical melodies are semantically unique items, and therefore, the neuroanatomical substrate underlying naming famous musical melodies is similar to naming other semantically unique items. The left temporal pole (LTP) is a region that is involved in the ability to name semantically unique entities, such as famous faces and landmarks. In a seminal study, Damasio et al. (1996) found that patients with lesions to the left temporal pole were impaired at naming the faces of famous people, but not animals or tools. Functional imaging research has confirmed that the left anterior temporal lobes selectively respond to person-knowledge, as opposed to more general categories of objects (Simmons et al., 2010). Additionally, Tranel (2006) found that patients with LTP damage were impaired at naming famous landmarks (and famous faces), suggesting that the LTP is not just necessary for naming of unique faces, but for multiple categories of semantically unique items. More recently, Drane et al., (2008, 2012) found that patients with left temporal lobectomies were significantly impaired at naming famous faces, while patients with right temporal lobectomies were significantly impaired at recognizing famous faces. These findings are consistent with functional imaging research (Damasio et al., 1996; Grabowski et al., 2001; Griffith et al., 2006; Nielson et al., 2010). Such findings have led to a theoretical framework positing that the LTP is a convergence zone that connects the retrieval of conceptual information about a unique item with the retrieval of the name of that item (Damasio et al., 2004; Tranel et al., 2001; Tranel et al., 2005). Lesions to the left temporal pole disrupt this connection between conceptual information and lexical information, and result in impairments in naming semantically unique items. Although previous research posits that the LTP is necessary for naming semantically unique entities, it is unclear whether or not musical melodies, which are an auditory stimulus, will be neuroanatomically represented in the same way as other unique entities. Tranel et al. (2005) investigated the naming of concrete (but not unique) entities using both visual and auditory stimuli. In a PET experiment, participants named various tools and animals that were presented either with a picture of the tool/animal or the sound that the tool/animal makes. Naming from both visual and auditory stimuli resulted in similar activations in the inferotemporal region – specifically, the locus of activation differed for the categories (animals v. tools) but not for the sensory modalities (visual v. auditory). While this task did not include naming of semantically unique entities, it provides support for the hypothesis that naming of auditory stimuli may engage similar brain regions to naming of visual stimuli. The study reported here expands on the previous framework that the left temporal pole is necessary for the naming of unique entities, irrespective of sensory modality or stimulus category, by investigating whether LTP damage is associated with impaired naming of a unique stimulus category: famous musical melodies. Additionally, we expand on the previous literature in music naming and recognition by proposing a specific, focal brain region that, when lesioned, will result in impairment in naming famous musical melodies. We hypothesized that the left temporal pole is associated with retrieving names for specific musical melodies, but not with retrieving semantic knowledge about these melodies. On this basis of this hypothesis, we predicted that: (1) Lesions to the LTP will impair naming of famous musical melodies, and (2) Lesions to the LTP will not impair recognition of famous musical melodies.