Background. Aphasia is a linguistic disorder that occurs after language acquisition and is most commonly caused by stroke. Research on novel word acquisition can contribute to the development of aphasia rehabilitation because it helps understand the relearning of words lost due to aphasia. Novel word acquisition has been researched mainly in chronic aphasia, in which learning is possible but shows large individual variation. There is initial evidence that novel word learning is also possible in non-chronic aphasia. Aims. The objective of this thesis is to study recovery and novel word learning in the subacute and chronic stages of aphasia. The thesis will also look into possible connections between learning in subacute aphasia and learning in chronic aphasia. These connections have not been previously explored. Methods. The multiple case study included four aphasic participants who were examined 0–3 months after stroke and again 12 months after stroke. The examination consisted of cognitive-linguistic background tests, questionnaires and a computer-based novel word learning task. In the latter, the participant was tasked with learning the associations between given pseudo-words and images through feedback and repetition. Research data was analyzed case by case. Results and conclusions. Recovery and novel word learning in subacute and chronic aphasia varied among the participants. In both stages, some participants learned new vocabulary and were able to transfer it into their long-term memory. The changes in novel word learning from subacute to chronic aphasia also varied among the subjects. These changes were not systematically connected with the severity of the participants’ aphasia, their baseline learning ability or an alleviation of cognitive-linguistic symptoms. Learning ability in subacute aphasia does therefore not always appear to predict learning ability in chronic aphasia, but novel word learning is possible in both subacute and chronic aphasia. Aphasia recovery shows considerable individual variation.

Background. Aphasia refers to a disability in the processing of linguistic information. It is most typically due to a stroke. Aphasia impairs a person's ability to understand, produce and use language. Recovery from aphasia is generally divided into three main stages: acute, subacute and chronic. So far, the ability to learn new words in aphasia has only been studied in chronic aphasia. Learning new words is a complex process. In natural language learning, the relationship between a word and its meaning is often not unambiguous, but the words and their possible meanings are numerous, and the connections are complex. The learning of new words can take place by hearing or by reading. The prerequisite for rehabilitation from aphasia is the ability to learn new things, but aphasia research typically uses familiar and everyday words. However, the use of familiar words in research makes it difficult to interpret the results. In order to assess whether a person with aphasia is able to learn new vocabulary, research must be done on a vocabulary that was not available to the person before aphasia. Objectives. The aim of this thesis is to determine, whether people with subacute aphasia can learn novel vocabulary in a situation that imitates natural language learning. This thesis also investigates how the learning ability of people with aphasia compares to the learning ability of healthy matched controls in the same task and how the matched controls learn compared to healthy young adults. Methods. The participants of the study consisted of three groups: young controls, matched controls and aphasic participants. The aphasic participants were examined at HUS Hospital District in Laakso Hospital in Helsinki and in Hyvinkää Hospital. The word learning task consisted of six 3-syllable nonwords that were practiced using a computer program. The task was to combine a spoken and written novel word with the correct novel image, choosing from two different images. Results and conclusions. Learning novel words is possible in subacute aphasia. However, there was great variability in the ability to learn between the aphasic participants. Some learned the words well, others learned some words, and some did not seem to learn the words at all. In addition, some of aphasic participants in the subacute stage were able to maintain the vocabulary they learned for at least a week after learning. Some of the aphasic participants learned the words on par with matched controls but for some the learning was significantly weaker. Both young adults and matched controls performed well on the learning task, but young adults learn the words faster than matched controls.