Research and development expenses in our Brooks Life Sciences Services segment were $2.8 million and $8.4 million, respectively, during the three and nine months ended June 30, 2021, as compared to $2.4 million and $6.7 million, respectively, during the corresponding periods of the prior fiscal year. The increase of $0.4 million and $1.7 million, respectively, during the three and nine months ended June 30, 2021 as compared to the corresponding period of fiscal year 2020 was primarily driven by higher payroll related costs and project costs.
Selling, General and Administrative Expenses
Selling, general and administrative expenses were $75.9 million for the three months ended June 30, 2021, as compared to $59.7 million for the corresponding period of the prior fiscal year. The increase of $16.2 million was driven by $10.2 million from segment selling, general and administrative expenses, $5.9 million from corporate expenses not allocated to our segments and $1.0 million of incremental costs related to acquisitions. The segment selling, general and administrative expenses are discussed in further detail below. The increase in unallocated corporate expenses was primarily driven by mergers and acquisition related expenses, which were $6.3 million for the three months ended June 30, 2021, compared to nominal charges for the three months ended June 30, 2020. Merger and acquisition expenses for the three months ended June 30, 2021 included $5.8 million of costs related to the separation of the Company. Unallocated corporate expenses also include amortization primarily related to customer relationship intangible assets, which were $7.7 million and $7.6 million for the three months ended June 30, 2021 and 2020, respectively.
In connection with the announcement of the separation of our business into two publicly-traded companies, we announced that the Automation company will retain the Brooks Automation, Inc. name and the Life Sciences company will be rebranded at the time of the separation. In connection with the rebranding, management is assessing the utility, remaining useful life and fair values of the Life Sciences trademark and tradename assets. The total net book value of these intangible assets is $14.3 million as of June 30, 2021. The conclusion of management’s assessment of the impact of the rebranding could result in an impairment charge of the asset values or an acceleration of amortization expense in future periods.
Selling, general and administrative expenses were $221.6 million for the nine months ended June 30, 2021, as compared to $178.9 million for the corresponding period of the prior fiscal year. The increase of $42.8 million was driven by $21.6 million from the segment selling, general and administrative expenses, $21.2 million from corporate expenses not allocated to our segments and $2.7 million of incremental costs related to acquisitions. The segment selling, general and administrative expenses are discussed in further detail below. The increase in unallocated corporate expenses was primarily driven by mergers and acquisition related expenses, which were $21.1 million for the nine months ended June 30, 2021, compared to $0.5 million for the nine months ended June 30, 2020. Merger and acquisition expenses for the nine months ended June 30, 2021 included $19.6 million of costs related to the separation of the Company. Unallocated corporate expenses also include amortization primarily related to customer relationship intangible assets, which were $22.7 million and $23.1 million for the nine months ended June 30, 2021 and 2020, respectively.
Selling, general and administrative expenses at the segment level, which are discussed below, include corporate allocations from shared corporate function which include finance, information technology, human resources, legal, executive, governance, logistics and compliance, and variable compensation. During the three and nine months ended June 30, 2021, corporate allocated expenses increased $3.8 million and $7.4 million respectively, compared to the corresponding prior periods, primarily due to higher variable compensation accruals and IT infrastructure costs.
Selling, general and administrative expenses in our Brooks Semiconductor Solutions Group segment were $25.7 million and $74.1 million, respectively, for the three and nine months ended June 30, 2021, as compared to $21.2 million and $65.0 million, respectively, for the corresponding periods of the prior fiscal year. The increase of $4.5 million and $9.1 million, respectively, for the three and nine months ended June 30, 2021 is primarily related to higher variable compensation expense and corporate allocated costs, which were driven by the factors discussed above, as well as the Precise acquisition which added $0.5 million of costs for the three and nine months ended June 30, 2021. These increases were partially offset by lower travel and trade show expenses.